---
layout: docs
title: SQL language
permalink: /docs/reference.html
---
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The page describes the SQL dialect recognized by Calcite's default SQL parser.

## Grammar

SQL grammar in [BNF](http://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form)-like
form.

{% highlight sql %}
statement:
      setStatement
  |   resetStatement
  |   explain
  |   describe
  |   insert
  |   update
  |   merge
  |   delete
  |   query

setStatement:
      [ ALTER ( SYSTEM | SESSION ) ] SET identifier '=' expression

resetStatement:
      [ ALTER ( SYSTEM | SESSION ) ] RESET identifier
  |   [ ALTER ( SYSTEM | SESSION ) ] RESET ALL

explain:
      EXPLAIN PLAN
      [ WITH TYPE | WITH IMPLEMENTATION | WITHOUT IMPLEMENTATION ]
      [ EXCLUDING ATTRIBUTES | INCLUDING [ ALL ] ATTRIBUTES ]
      FOR ( query | insert | update | merge | delete )

describe:
      DESCRIBE DATABASE databaseName
   |  DESCRIBE CATALOG [ databaseName . ] catalogName
   |  DESCRIBE SCHEMA [ [ databaseName . ] catalogName ] . schemaName
   |  DESCRIBE [ TABLE ] [ [ [ databaseName . ] catalogName . ] schemaName . ] tableName [ columnName ]
   |  DESCRIBE [ STATEMENT ] ( query | insert | update | merge | delete )

insert:
      ( INSERT | UPSERT ) INTO tablePrimary
      [ '(' column [, column ]* ')' ]
      query

update:
      UPDATE tablePrimary
      SET assign [, assign ]*
      [ WHERE booleanExpression ]

assign:
      identifier '=' expression

merge:
      MERGE INTO tablePrimary [ [ AS ] alias ]
      USING tablePrimary
      ON booleanExpression
      [ WHEN MATCHED THEN UPDATE SET assign [, assign ]* ]
      [ WHEN NOT MATCHED THEN INSERT VALUES '(' value [ , value ]* ')' ]

delete:
      DELETE FROM tablePrimary [ [ AS ] alias ]
      [ WHERE booleanExpression ]

query:
      values
  |   WITH withItem [ , withItem ]* query
  |   {
          select
      |   selectWithoutFrom
      |   query UNION [ ALL ] query
      |   query EXCEPT query
      |   query INTERSECT query
      }
      [ ORDER BY orderItem [, orderItem ]* ]
      [ LIMIT { count | ALL } ]
      [ OFFSET start { ROW | ROWS } ]
      [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ]

withItem:
      name
      [ '(' column [, column ]* ')' ]
      AS '(' query ')'

orderItem:
      expression [ ASC | DESC ] [ NULLS FIRST | NULLS LAST ]

select:
      SELECT [ STREAM ] [ ALL | DISTINCT ]
          { * | projectItem [, projectItem ]* }
      FROM tableExpression
      [ WHERE booleanExpression ]
      [ GROUP BY { groupItem [, groupItem ]* } ]
      [ HAVING booleanExpression ]
      [ WINDOW windowName AS windowSpec [, windowName AS windowSpec ]* ]

selectWithoutFrom:
      SELECT [ ALL | DISTINCT ]
          { * | projectItem [, projectItem ]* }

projectItem:
      expression [ [ AS ] columnAlias ]
  |   tableAlias . *

tableExpression:
      tableReference [, tableReference ]*
  |   tableExpression [ NATURAL ] [ LEFT | RIGHT | FULL ] JOIN tableExpression [ joinCondition ]

joinCondition:
      ON booleanExpression
  |   USING '(' column [, column ]* ')'

tableReference:
      tablePrimary
      [ [ AS ] alias [ '(' columnAlias [, columnAlias ]* ')' ] ]

tablePrimary:
      [ [ catalogName . ] schemaName . ] tableName
      '(' TABLE [ [ catalogName . ] schemaName . ] tableName ')'
  |   [ LATERAL ] '(' query ')'
  |   UNNEST '(' expression ')' [ WITH ORDINALITY ]
  |   [ LATERAL ] TABLE '(' [ SPECIFIC ] functionName '(' expression [, expression ]* ')' ')'

values:
      VALUES expression [, expression ]*

groupItem:
      expression
  |   '(' ')'
  |   '(' expression [, expression ]* ')'
  |   CUBE '(' expression [, expression ]* ')'
  |   ROLLUP '(' expression [, expression ]* ')'
  |   GROUPING SETS '(' groupItem [, groupItem ]* ')'

windowRef:
      windowName
  |   windowSpec

windowSpec:
      [ windowName ]
      '('
      [ ORDER BY orderItem [, orderItem ]* ]
      [ PARTITION BY expression [, expression ]* ]
      [
          RANGE numericOrIntervalExpression { PRECEDING | FOLLOWING }
      |   ROWS numericExpression { PRECEDING | FOLLOWING }
      ]
      ')'
{% endhighlight %}

In *merge*, at least one of the WHEN MATCHED and WHEN NOT MATCHED clauses must
be present.

In *orderItem*, if *expression* is a positive integer *n*, it denotes
the <em>n</em>th item in the SELECT clause.

An aggregate query is a query that contains a GROUP BY or a HAVING
clause, or aggregate functions in the SELECT clause. In the SELECT,
HAVING and ORDER BY clauses of an aggregate query, all expressions
must be constant within the current group (that is, grouping constants
as defined by the GROUP BY clause, or constants), or aggregate
functions, or a combination of constants and aggregate
functions. Aggregate and grouping functions may only appear in an
aggregate query, and only in a SELECT, HAVING or ORDER BY clause.

A scalar sub-query is a sub-query used as an expression.
If the sub-query returns no rows, the value is NULL; if it
returns more than one row, it is an error.

IN, EXISTS and scalar sub-queries can occur
in any place where an expression can occur (such as the SELECT clause,
WHERE clause, ON clause of a JOIN, or as an argument to an aggregate
function).

An IN, EXISTS or scalar sub-query may be correlated; that is, it
may refer to tables in the FROM clause of an enclosing query.

*selectWithoutFrom* is equivalent to VALUES,
but is not standard SQL and is only allowed in certain
[conformance levels]({{ site.apiRoot }}/org/apache/calcite/sql/validate/SqlConformance.html#isFromRequired--).

## Keywords

The following is a list of SQL keywords.
Reserved keywords are **bold**.

{% comment %} start {% endcomment %}
A,
**ABS**,
ABSOLUTE,
ACTION,
ADA,
ADD,
ADMIN,
AFTER,
**ALL**,
**ALLOCATE**,
**ALLOW**,
**ALTER**,
ALWAYS,
**AND**,
**ANY**,
**ARE**,
**ARRAY**,
**AS**,
ASC,
**ASENSITIVE**,
ASSERTION,
ASSIGNMENT,
**ASYMMETRIC**,
**AT**,
**ATOMIC**,
ATTRIBUTE,
ATTRIBUTES,
**AUTHORIZATION**,
**AVG**,
BEFORE,
**BEGIN**,
BERNOULLI,
**BETWEEN**,
**BIGINT**,
**BINARY**,
**BIT**,
**BLOB**,
**BOOLEAN**,
**BOTH**,
BREADTH,
**BY**,
C,
**CALL**,
**CALLED**,
**CARDINALITY**,
CASCADE,
**CASCADED**,
**CASE**,
**CAST**,
CATALOG,
CATALOG_NAME,
**CEIL**,
**CEILING**,
CENTURY,
CHAIN,
**CHAR**,
**CHARACTER**,
CHARACTERISTICTS,
CHARACTERS,
**CHARACTER_LENGTH**,
CHARACTER_SET_CATALOG,
CHARACTER_SET_NAME,
CHARACTER_SET_SCHEMA,
**CHAR_LENGTH**,
**CHECK**,
CLASS_ORIGIN,
**CLOB**,
**CLOSE**,
**COALESCE**,
COBOL,
**COLLATE**,
COLLATION,
COLLATION_CATALOG,
COLLATION_NAME,
COLLATION_SCHEMA,
**COLLECT**,
**COLUMN**,
COLUMN_NAME,
COMMAND_FUNCTION,
COMMAND_FUNCTION_CODE,
**COMMIT**,
COMMITTED,
**CONDITION**,
CONDITION_NUMBER,
**CONNECT**,
CONNECTION,
CONNECTION_NAME,
**CONSTRAINT**,
CONSTRAINTS,
CONSTRAINT_CATALOG,
CONSTRAINT_NAME,
CONSTRAINT_SCHEMA,
CONSTRUCTOR,
CONTAINS,
CONTINUE,
**CONVERT**,
**CORR**,
**CORRESPONDING**,
**COUNT**,
**COVAR_POP**,
**COVAR_SAMP**,
**CREATE**,
**CROSS**,
**CUBE**,
**CUME_DIST**,
**CURRENT**,
**CURRENT_CATALOG**,
**CURRENT_DATE**,
**CURRENT_DEFAULT_TRANSFORM_GROUP**,
**CURRENT_PATH**,
**CURRENT_ROLE**,
**CURRENT_SCHEMA**,
**CURRENT_TIME**,
**CURRENT_TIMESTAMP**,
**CURRENT_TRANSFORM_GROUP_FOR_TYPE**,
**CURRENT_USER**,
**CURSOR**,
CURSOR_NAME,
**CYCLE**,
DATA,
DATABASE,
**DATE**,
DATETIME_INTERVAL_CODE,
DATETIME_INTERVAL_PRECISION,
**DAY**,
**DEALLOCATE**,
**DEC**,
DECADE,
**DECIMAL**,
**DECLARE**,
**DEFAULT**,
DEFAULTS,
DEFERRABLE,
DEFERRED,
DEFINED,
DEFINER,
DEGREE,
**DELETE**,
**DENSE_RANK**,
DEPTH,
**DEREF**,
DERIVED,
DESC,
**DESCRIBE**,
DESCRIPTION,
DESCRIPTOR,
**DETERMINISTIC**,
DIAGNOSTICS,
**DISALLOW**,
**DISCONNECT**,
DISPATCH,
**DISTINCT**,
DOMAIN,
**DOUBLE**,
DOW,
DOY,
**DROP**,
**DYNAMIC**,
DYNAMIC_FUNCTION,
DYNAMIC_FUNCTION_CODE,
**EACH**,
**ELEMENT**,
**ELSE**,
**END**,
**END-EXEC**,
EPOCH,
EQUALS,
**ESCAPE**,
**EVERY**,
**EXCEPT**,
EXCEPTION,
EXCLUDE,
EXCLUDING,
**EXEC**,
**EXECUTE**,
**EXISTS**,
**EXP**,
**EXPLAIN**,
**EXTEND**,
**EXTERNAL**,
**EXTRACT**,
**FALSE**,
**FETCH**,
**FILTER**,
FINAL,
FIRST,
**FIRST_VALUE**,
**FLOAT**,
**FLOOR**,
FOLLOWING,
**FOR**,
**FOREIGN**,
FORTRAN,
FOUND,
FRAC_SECOND,
**FREE**,
**FROM**,
**FULL**,
**FUNCTION**,
**FUSION**,
G,
GENERAL,
GENERATED,
**GET**,
**GLOBAL**,
GO,
GOTO,
**GRANT**,
GRANTED,
**GROUP**,
**GROUPING**,
**HAVING**,
HIERARCHY,
**HOLD**,
**HOUR**,
**IDENTITY**,
IMMEDIATE,
IMPLEMENTATION,
**IMPORT**,
**IN**,
INCLUDING,
INCREMENT,
**INDICATOR**,
INITIALLY,
**INNER**,
**INOUT**,
INPUT,
**INSENSITIVE**,
**INSERT**,
INSTANCE,
INSTANTIABLE,
**INT**,
**INTEGER**,
**INTERSECT**,
**INTERSECTION**,
**INTERVAL**,
**INTO**,
INVOKER,
**IS**,
ISOLATION,
JAVA,
**JOIN**,
K,
KEY,
KEY_MEMBER,
KEY_TYPE,
LABEL,
**LANGUAGE**,
**LARGE**,
LAST,
**LAST_VALUE**,
**LATERAL**,
**LEADING**,
**LEFT**,
LENGTH,
LEVEL,
LIBRARY,
**LIKE**,
**LIMIT**,
**LN**,
**LOCAL**,
**LOCALTIME**,
**LOCALTIMESTAMP**,
LOCATOR,
**LOWER**,
M,
MAP,
**MATCH**,
MATCHED,
**MAX**,
MAXVALUE,
**MEMBER**,
**MERGE**,
MESSAGE_LENGTH,
MESSAGE_OCTET_LENGTH,
MESSAGE_TEXT,
**METHOD**,
MICROSECOND,
MILLENNIUM,
**MIN**,
**MINUTE**,
MINVALUE,
**MOD**,
**MODIFIES**,
**MODULE**,
**MONTH**,
MORE,
**MULTISET**,
MUMPS,
NAME,
NAMES,
**NATIONAL**,
**NATURAL**,
**NCHAR**,
**NCLOB**,
NESTING,
**NEW**,
**NEXT**,
**NO**,
**NONE**,
**NORMALIZE**,
NORMALIZED,
**NOT**,
**NULL**,
NULLABLE,
**NULLIF**,
NULLS,
NUMBER,
**NUMERIC**,
OBJECT,
OCTETS,
**OCTET_LENGTH**,
**OF**,
**OFFSET**,
**OLD**,
**ON**,
**ONLY**,
**OPEN**,
OPTION,
OPTIONS,
**OR**,
**ORDER**,
ORDERING,
ORDINALITY,
OTHERS,
**OUT**,
**OUTER**,
OUTPUT,
**OVER**,
**OVERLAPS**,
**OVERLAY**,
OVERRIDING,
PAD,
**PARAMETER**,
PARAMETER_MODE,
PARAMETER_NAME,
PARAMETER_ORDINAL_POSITION,
PARAMETER_SPECIFIC_CATALOG,
PARAMETER_SPECIFIC_NAME,
PARAMETER_SPECIFIC_SCHEMA,
PARTIAL,
**PARTITION**,
PASCAL,
PASSTHROUGH,
PATH,
**PERCENTILE_CONT**,
**PERCENTILE_DISC**,
**PERCENT_RANK**,
PLACING,
PLAN,
PLI,
**POSITION**,
**POWER**,
PRECEDING,
**PRECISION**,
**PREPARE**,
PRESERVE,
**PRIMARY**,
PRIOR,
PRIVILEGES,
**PROCEDURE**,
PUBLIC,
QUARTER,
**RANGE**,
**RANK**,
READ,
**READS**,
**REAL**,
**RECURSIVE**,
**REF**,
**REFERENCES**,
**REFERENCING**,
**REGR_AVGX**,
**REGR_AVGY**,
**REGR_COUNT**,
**REGR_INTERCEPT**,
**REGR_R2**,
**REGR_SLOPE**,
**REGR_SXX**,
**REGR_SXY**,
**REGR_SYY**,
RELATIVE,
**RELEASE**,
REPEATABLE,
**RESET**,
RESTART,
RESTRICT,
**RESULT**,
**RETURN**,
RETURNED_CARDINALITY,
RETURNED_LENGTH,
RETURNED_OCTET_LENGTH,
RETURNED_SQLSTATE,
**RETURNS**,
**REVOKE**,
**RIGHT**,
ROLE,
**ROLLBACK**,
**ROLLUP**,
ROUTINE,
ROUTINE_CATALOG,
ROUTINE_NAME,
ROUTINE_SCHEMA,
**ROW**,
**ROWS**,
ROW_COUNT,
**ROW_NUMBER**,
**SAVEPOINT**,
SCALE,
SCHEMA,
SCHEMA_NAME,
**SCOPE**,
SCOPE_CATALOGS,
SCOPE_NAME,
SCOPE_SCHEMA,
**SCROLL**,
**SEARCH**,
**SECOND**,
SECTION,
SECURITY,
**SELECT**,
SELF,
**SENSITIVE**,
SEQUENCE,
SERIALIZABLE,
SERVER,
SERVER_NAME,
SESSION,
**SESSION_USER**,
**SET**,
SETS,
**SIMILAR**,
SIMPLE,
SIZE,
**SMALLINT**,
**SOME**,
SOURCE,
SPACE,
**SPECIFIC**,
**SPECIFICTYPE**,
SPECIFIC_NAME,
**SQL**,
**SQLEXCEPTION**,
**SQLSTATE**,
**SQLWARNING**,
SQL_TSI_DAY,
SQL_TSI_FRAC_SECOND,
SQL_TSI_HOUR,
SQL_TSI_MICROSECOND,
SQL_TSI_MINUTE,
SQL_TSI_MONTH,
SQL_TSI_QUARTER,
SQL_TSI_SECOND,
SQL_TSI_WEEK,
SQL_TSI_YEAR,
**SQRT**,
**START**,
STATE,
STATEMENT,
**STATIC**,
**STDDEV_POP**,
**STDDEV_SAMP**,
**STREAM**,
STRUCTURE,
STYLE,
SUBCLASS_ORIGIN,
**SUBMULTISET**,
SUBSTITUTE,
**SUBSTRING**,
**SUM**,
**SYMMETRIC**,
**SYSTEM**,
**SYSTEM_USER**,
**TABLE**,
**TABLESAMPLE**,
TABLE_NAME,
TEMPORARY,
**THEN**,
TIES,
**TIME**,
**TIMESTAMP**,
TIMESTAMPADD,
TIMESTAMPDIFF,
**TIMEZONE_HOUR**,
**TIMEZONE_MINUTE**,
**TINYINT**,
**TO**,
TOP_LEVEL_COUNT,
**TRAILING**,
TRANSACTION,
TRANSACTIONS_ACTIVE,
TRANSACTIONS_COMMITTED,
TRANSACTIONS_ROLLED_BACK,
TRANSFORM,
TRANSFORMS,
**TRANSLATE**,
**TRANSLATION**,
**TREAT**,
**TRIGGER**,
TRIGGER_CATALOG,
TRIGGER_NAME,
TRIGGER_SCHEMA,
**TRIM**,
**TRUE**,
TYPE,
**UESCAPE**,
UNBOUNDED,
UNCOMMITTED,
UNDER,
**UNION**,
**UNIQUE**,
**UNKNOWN**,
UNNAMED,
**UNNEST**,
**UPDATE**,
**UPPER**,
**UPSERT**,
USAGE,
**USER**,
USER_DEFINED_TYPE_CATALOG,
USER_DEFINED_TYPE_CODE,
USER_DEFINED_TYPE_NAME,
USER_DEFINED_TYPE_SCHEMA,
**USING**,
**VALUE**,
**VALUES**,
**VARBINARY**,
**VARCHAR**,
**VARYING**,
**VAR_POP**,
**VAR_SAMP**,
VERSION,
VIEW,
WEEK,
**WHEN**,
**WHENEVER**,
**WHERE**,
**WIDTH_BUCKET**,
**WINDOW**,
**WITH**,
**WITHIN**,
**WITHOUT**,
WORK,
WRAPPER,
WRITE,
XML,
**YEAR**,
ZONE.
{% comment %} end {% endcomment %}

## Identifiers

Identifiers are the names of tables, columns and other metadata
elements used in a SQL query.

Unquoted identifiers, such as emp, must start with a letter and can
only contain letters, digits, and underscores. They are implicitly
converted to upper case.

Quoted identifiers, such as `"Employee Name"`, start and end with
double quotes.  They may contain virtually any character, including
spaces and other punctuation.  If you wish to include a double quote
in an identifier, use another double quote to escape it, like this:
`"An employee called ""Fred""."`.

In Calcite, matching identifiers to the name of the referenced object is
case-sensitive.  But remember that unquoted identifiers are implicitly
converted to upper case before matching, and if the object it refers
to was created using an unquoted identifier for its name, then its
name will have been converted to upper case also.

## Data types

### Scalar types

| Data type   | Description               | Range and examples   |
|:----------- |:------------------------- |:---------------------|
| BOOLEAN     | Logical values            | Values: TRUE, FALSE, UNKNOWN
| TINYINT     | 1 byte signed integer     | Range is -255 to 256
| SMALLINT    | 2 byte signed integer     | Range is -32768 to 32767
| INTEGER, INT | 4 byte signed integer    | Range is -2147483648 to 2147483647
| BIGINT      | 8 byte signed integer     | Range is -9223372036854775808 to 9223372036854775807
| DECIMAL(p, s) | Fixed point             | Example: 123.45 is a DECIMAL(5, 2) value.
| NUMERIC     | Fixed point               |
| REAL, FLOAT | 4 byte floating point     | 6 decimal digits precision
| DOUBLE      | 8 byte floating point     | 15 decimal digits precision
| CHAR(n), CHARACTER(n) | Fixed-width character string | 'Hello', '' (empty string), _latin1'Hello', n'Hello', _UTF16'Hello', 'Hello' 'there' (literal split into multiple parts)
| VARCHAR(n), CHARACTER VARYING(n) | Variable-length character string | As CHAR(n)
| BINARY(n)   | Fixed-width binary string | x'45F0AB', x'' (empty binary string), x'AB' 'CD' (multi-part binary string literal)
| VARBINARY(n), BINARY VARYING(n) | Variable-length binary string | As BINARY(n)
| DATE        | Date                      | Example: DATE '1969-07-20'
| TIME        | Time of day               | Example: TIME '20:17:40'
| TIMESTAMP [ WITHOUT TIME ZONE ] | Date and time | Example: TIMESTAMP '1969-07-20 20:17:40'
| TIMESTAMP WITH TIME ZONE | Date and time with time zone | Example: TIMESTAMP '1969-07-20 20:17:40 America/Los Angeles'
| INTERVAL timeUnit [ TO timeUnit ] | Date time interval | Examples: INTERVAL '1:5' YEAR TO MONTH, INTERVAL '45' DAY
| Anchored interval | Date time interval  | Example: (DATE '1969-07-20', DATE '1972-08-29')

Where:

{% highlight sql %}
timeUnit:
  MILLENNIUM | CENTURY | DECADE | YEAR | QUARTER | MONTH | WEEK | DOY | DOW | DAY | HOUR | MINUTE | SECOND | EPOCH
{% endhighlight %}

Note:

* DATE, TIME and TIMESTAMP have no time zone. There is not even an implicit
  time zone, such as UTC (as in Java) or the local time zone. It is left to
  the user or application to supply a time zone.

### Non-scalar types

| Type     | Description
|:-------- |:-----------------------------------------------------------
| ANY      | A value of an unknown type
| ROW      | Row with 1 or more columns
| MAP      | Collection of keys mapped to values
| MULTISET | Unordered collection that may contain duplicates
| ARRAY    | Ordered, contiguous collection that may contain duplicates
| CURSOR   | Cursor over the result of executing a query

## Operators and functions

### Operator precedence

The operator precedence and associativity, highest to lowest.

| Operator                                          | Associativity
|:------------------------------------------------- |:-------------
| .                                                 | left
| [ ] (array element)                               | left
| + - (unary plus, minus)                           | right
| * /                                               | left
| + -                                               | left
| BETWEEN, IN, LIKE, SIMILAR                        | -
| < > = <= >= <>                                    | left
| IS NULL, IS FALSE, IS NOT TRUE etc.               | -
| NOT                                               | right
| AND                                               | left
| OR                                                | left

### Comparison operators

| Operator syntax                                   | Description
|:------------------------------------------------- |:-----------
| value1 = value2                                   | Equals
| value1 <> value2                                  | Not equal
| value1 > value2                                   | Greater than
| value1 >= value2                                  | Greater than or equal
| value1 < value2                                   | Less than
| value1 <= value2                                  | Less than or equal
| value IS NULL                                     | Whether *value* is null
| value IS NOT NULL                                 | Whether *value* is not null
| value1 IS DISTINCT FROM value2                    | Whether two values are not equal, treating null values as the same
| value1 IS NOT DISTINCT FROM value2                | Whether two values are equal, treating null values as the same
| value1 BETWEEN value2 AND value3                  | Whether *value1* is greater than or equal to *value2* and less than or equal to *value3*
| value1 NOT BETWEEN value2 AND value3              | Whether *value1* is less than *value2* or greater than *value3*
| string1 LIKE string2 [ ESCAPE string3 ]           | Whether *string1* matches pattern *string2*
| string1 NOT LIKE string2 [ ESCAPE string3 ]       | Whether *string1* does not match pattern *string2*
| string1 SIMILAR TO string2 [ ESCAPE string3 ]     | Whether *string1* matches regular expression *string2*
| string1 NOT SIMILAR TO string2 [ ESCAPE string3 ] | Whether *string1* does not match regular expression *string2*
| value IN (value [, value]* )                      | Whether *value* is equal to a value in a list
| value NOT IN (value [, value]* )                  | Whether *value* is not equal to every value in a list
| value IN (sub-query)                              | Whether *value* is equal to a row returned by *sub-query*
| value NOT IN (sub-query)                          | Whether *value* is not equal to every row returned by *sub-query*
| EXISTS (sub-query)                                | Whether *sub-query* returns at least one row

### Logical operators

| Operator syntax        | Description
|:---------------------- |:-----------
| boolean1 OR boolean2   | Whether *boolean1* is TRUE or *boolean2* is TRUE
| boolean1 AND boolean2  | Whether *boolean1* and *boolean2* are both TRUE
| NOT boolean            | Whether *boolean* is not TRUE; returns UNKNOWN if *boolean* is UNKNOWN
| boolean IS FALSE       | Whether *boolean* is FALSE; returns FALSE if *boolean* is UNKNOWN
| boolean IS NOT FALSE   | Whether *boolean* is not FALSE; returns TRUE if *boolean* is UNKNOWN
| boolean IS TRUE        | Whether *boolean* is TRUE; returns FALSE if *boolean* is UNKNOWN
| boolean IS NOT TRUE    | Whether *boolean* is not TRUE; returns TRUE if *boolean* is UNKNOWN
| boolean IS UNKNOWN     | Whether *boolean* is UNKNOWN
| boolean IS NOT UNKNOWN | Whether *boolean* is not UNKNOWN

### Arithmetic operators and functions

| Operator syntax           | Description
|:------------------------- |:-----------
| + numeric                 | Returns *numeric*
|:- numeric                 | Returns negative *numeric*
| numeric1 + numeric2       | Returns *numeric1* plus *numeric2*
| numeric1 - numeric2       | Returns *numeric1* minus *numeric2*
| numeric1 * numeric2       | Returns *numeric1* multiplied by *numeric2*
| numeric1 / numeric2       | Returns *numeric1* divided by *numeric2*
| POWER(numeric1, numeric2) | Returns *numeric1* raised to the power of *numeric2*
| ABS(numeric)              | Returns the absolute value of *numeric*
| MOD(numeric, numeric)     | Returns the remainder (modulus) of *numeric1* divided by *numeric2*. The result is negative only if *numeric1* is negative
| SQRT(numeric)             | Returns the square root of *numeric*
| LN(numeric)               | Returns the natural logarithm (base *e*) of *numeric*
| LOG10(numeric)            | Returns the base 10 logarithm of *numeric*
| EXP(numeric)              | Returns *e* raised to the power of *numeric*
| CEIL(numeric)             | Rounds *numeric* up, and returns the smallest number that is greater than or equal to *numeric*
| FLOOR(numeric)            | Rounds *numeric* down, and returns the largest number that is less than or equal to *numeric*

### Character string operators and functions

| Operator syntax            | Description
|:-------------------------- |:-----------
| string &#124;&#124; string | Concatenates two character strings.
| CHAR_LENGTH(string)        | Returns the number of characters in a character string
| CHARACTER_LENGTH(string)   | As CHAR_LENGTH(*string*)
| UPPER(string)              | Returns a character string converted to upper case
| LOWER(string)              | Returns a character string converted to lower case
| POSITION(string1 IN string2) | Returns the position of the first occurrence of *string1* in *string2*
| TRIM( { BOTH &#124; LEADING &#124; TRAILING } string1 FROM string2) | Removes the longest string containing only the characters in *string1* from the start/end/both ends of *string1*
| OVERLAY(string1 PLACING string2 FROM integer [ FOR integer2 ]) | Replaces a substring of *string1* with *string2*
| SUBSTRING(string FROM integer)  | Returns a substring of a character string starting at a given point.
| SUBSTRING(string FROM integer FOR integer) | Returns a substring of a character string starting at a given point with a given length.
| INITCAP(string)            | Returns *string* with the first letter of each word converter to upper case and the rest to lower case. Words are sequences of alphanumeric characters separated by non-alphanumeric characters.

Not implemented:

* SUBSTRING(string FROM regexp FOR regexp)

### Binary string operators and functions

| Operator syntax | Description
|:--------------- |:-----------
| binary &#124;&#124; binary | Concatenates two binary strings.
| POSITION(binary1 IN binary2) | Returns the position of the first occurrence of *binary1* in *binary2*
| OVERLAY(binary1 PLACING binary2 FROM integer [ FOR integer2 ]) | Replaces a substring of *binary1* with *binary2*
| SUBSTRING(binary FROM integer) | Returns a substring of *binary* starting at a given point
| SUBSTRING(binary FROM integer FOR integer) | Returns a substring of *binary* starting at a given point with a given length

### Date/time functions

| Operator syntax           | Description
|:------------------------- |:-----------
| LOCALTIME                 | Returns the current date and time in the session time zone in a value of datatype TIME
| LOCALTIME(precision)      | Returns the current date and time in the session time zone in a value of datatype TIME, with *precision* digits of precision
| LOCALTIMESTAMP            | Returns the current date and time in the session time zone in a value of datatype TIMESTAMP
| LOCALTIMESTAMP(precision) | Returns the current date and time in the session time zone in a value of datatype TIMESTAMP, with *precision* digits of precision
| CURRENT_TIME              | Returns the current time in the session time zone, in a value of datatype TIMESTAMP WITH TIME ZONE
| CURRENT_DATE              | Returns the current date in the session time zone, in a value of datatype DATE
| CURRENT_TIMESTAMP         | Returns the current date and time in the session time zone, in a value of datatype TIMESTAMP WITH TIME ZONE
| EXTRACT(timeUnit FROM datetime) | Extracts and returns the value of a specified datetime field from a datetime value expression
| FLOOR(datetime TO timeUnit) | Rounds *datetime* down to *timeUnit*
| CEIL(datetime TO timeUnit) | Rounds *datetime* up to *timeUnit*

Not implemented:

* EXTRACT(timeUnit FROM interval)
* CEIL(interval)
* FLOOR(interval)
* datetime - datetime timeUnit [ TO timeUnit ]
* interval OVERLAPS interval
* \+ interval
* \- interval
* interval + interval
* interval - interval
* interval / interval
* datetime + interval
* datetime - interval

### System functions

| Operator syntax | Description
|:--------------- |:-----------
| USER            | Equivalent to CURRENT_USER
| CURRENT_USER    | User name of current execution context
| SESSION_USER    | Session user name
| SYSTEM_USER     | Returns the name of the current data store user as identified by the operating system
| CURRENT_PATH    | Returns a character string representing the current lookup scope for references to user-defined routines and types
| CURRENT_ROLE    | Returns the current active role

### Conditional functions and operators

| Operator syntax | Description
|:--------------- |:-----------
| CASE value<br/>WHEN value1 [, value11 ]* THEN result1<br/>[ WHEN valueN [, valueN1 ]* THEN resultN ]*<br/>[ ELSE resultZ ]<br/> END | Simple case
| CASE<br/>WHEN condition1 THEN result1<br/>[ WHEN conditionN THEN resultN ]*<br/>[ ELSE resultZ ]<br/>END | Searched case
| NULLIF(value, value) | Returns NULL if the values are the same.<br/><br/>For example, <code>NULLIF(5, 5)</code> returns NULL; <code>NULLIF(5, 0)</code> returns 5.
| COALESCE(value, value [, value ]* ) | Provides a value if the first value is null.<br/><br/>For example, <code>COALESCE(NULL, 5)</code> returns 5.

### Type conversion

| Operator syntax | Description
|:--------------- | :----------
| CAST(value AS type) | Converts a value to a given type.

### Value constructors

| Operator syntax | Description
|:--------------- |:-----------
| ROW (value [, value]* ) | Creates a row from a list of values.
| (value [, value]* )     | Creates a row from a list of values.
| map '[' key ']'     | Returns the element of a map with a particular key.
| array '[' index ']' | Returns the element at a particular location in an array.
| ARRAY '[' value [, value ]* ']' | Creates an array from a list of values.
| MAP '[' key, value [, key, value ]* ']' | Creates a map from a list of key-value pairs.

### Collection functions

| Operator syntax | Description
|:--------------- |:-----------
| ELEMENT(value)  | Returns the sole element of a array or multiset; null if the collection is empty; throws if it has more than one element.
| CARDINALITY(value) | Returns the number of elements in an array or multiset.

See also: UNNEST relational operator converts a collection to a relation.

### JDBC function escape

#### Numeric

| Operator syntax                | Description
|:------------------------------ |:-----------
| {fn ABS(numeric)}              | Returns the absolute value of *numeric*
| {fn EXP(numeric)}              | Returns *e* raised to the power of *numeric*
| {fn LOG(numeric)}              | Returns the natural logarithm (base *e*) of *numeric*
| {fn LOG10(numeric)}            | Returns the base-10 logarithm of *numeric*
| {fn MOD(numeric1, numeric2)}   | Returns the remainder (modulus) of *numeric1* divided by *numeric2*. The result is negative only if *numeric1* is negative
| {fn POWER(numeric1, numeric2)} | Returns *numeric1* raised to the power of *numeric2*

Not implemented:

* {fn ACOS(numeric)} - Returns the arc cosine of *numeric*
* {fn ASIN(numeric)} - Returns the arc sine of *numeric*
* {fn ATAN(numeric)} - Returns the arc tangent of *numeric*
* {fn ATAN2(numeric, numeric)}
* {fn CEILING(numeric)} - Rounds *numeric* up, and returns the smallest number that is greater than or equal to *numeric*
* {fn COS(numeric)} - Returns the cosine of *numeric*
* {fn COT(numeric)}
* {fn DEGREES(numeric)} - Converts *numeric* from radians to degrees
* {fn FLOOR(numeric)} - Rounds *numeric* down, and returns the largest number that is less than or equal to *numeric*
* {fn PI()} - Returns a value that is closer than any other value to *pi*
* {fn RADIANS(numeric)} - Converts *numeric* from degrees to radians
* {fn RAND(numeric)}
* {fn ROUND(numeric, numeric)}
* {fn SIGN(numeric)}
* {fn SIN(numeric)} - Returns the sine of *numeric*
* {fn SQRT(numeric)} - Returns the square root of *numeric*
* {fn TAN(numeric)} - Returns the tangent of *numeric*
* {fn TRUNCATE(numeric, numeric)}

#### String

| Operator syntax | Description
|:--------------- |:-----------
| {fn CONCAT(character, character)} | Returns the concatenation of character strings
| {fn LOCATE(string1, string2)} | Returns the position in *string2* of the first occurrence of *string1*. Searches from the beginning of the second CharacterExpression, unless the startIndex parameter is specified.
| {fn INSERT(string1, start, length, string2)} | Inserts *string2* into a slot in *string1*
| {fn LCASE(string)}            | Returns a string in which all alphabetic characters in *string* have been converted to lower case
| {fn LENGTH(string)} | Returns the number of characters in a string
| {fn LOCATE(string1, string2 [, integer])} | Returns the position in *string2* of the first occurrence of *string1*. Searches from the beginning of *string2*, unless *integer* is specified.
| {fn LTRIM(string)} | Returns *string* with leading space characters removed
| {fn RTRIM(string)} | Returns *string* with trailing space characters removed
| {fn SUBSTRING(string, offset, length)} | Returns a character string that consists of *length* characters from *string* starting at the *offset* position
| {fn UCASE(string)} | Returns a string in which all alphabetic characters in *string* have been converted to upper case

Not implemented:

* {fn ASCII(string)} - Convert a single-character string to the corresponding ASCII code, an integer between 0 and 255
* {fn CHAR(string)}
* {fn DIFFERENCE(string, string)}
* {fn LEFT(string, integer)}
* {fn REPEAT(string, integer)}
* {fn REPLACE(string, string, string)}
* {fn RIGHT(string, integer)}
* {fn SOUNDEX(string)}
* {fn SPACE(integer)}

#### Date/time

| Operator syntax | Description
|:--------------- |:-----------
| {fn CURDATE()}  | Equivalent to `CURRENT_DATE`
| {fn CURTIME()}  | Equivalent to `LOCALTIME`
| {fn NOW()}      | Equivalent to `LOCALTIMESTAMP`
| {fn QUARTER(date)} | Equivalent to `EXTRACT(QUARTER FROM date)`. Returns an integer between 1 and 4.
| {fn TIMESTAMPADD(timeUnit, count, timestamp)} | Adds an interval of *count* *timeUnit*s to a timestamp
| {fn TIMESTAMPDIFF(timeUnit, timestamp1, timestamp2)} | Subtracts *timestamp1* from *timestamp2* and returns the result in *timeUnit*s

Not implemented:

* {fn DAYNAME(date)}
* {fn DAYOFMONTH(date)}
* {fn DAYOFWEEK(date)}
* {fn DAYOFYEAR(date)}
* {fn HOUR(time)}
* {fn MINUTE(time)}
* {fn MONTH(date)}
* {fn MONTHNAME(date)}
* {fn SECOND(time)}
* {fn WEEK(date)}
* {fn YEAR(date)}

#### System

Not implemented:

* {fn DATABASE()}
* {fn IFNULL(value, value)}
* {fn USER(value, value)}
* {fn CONVERT(value, type)}

### Aggregate functions

Syntax:

{% highlight sql %}
aggregateCall:
        agg( [ DISTINCT ] value [, value]* ) [ FILTER ( WHERE condition ) ]
    |   agg(*) [ FILTER ( WHERE condition ) ]
{% endhighlight %}

If `FILTER` is present, the aggregate function only considers rows for which
*condition* evaluates to TRUE.

If `DISTINCT` is present, duplicate argument values are eliminated before being
passed to the aggregate function.

| Operator syntax                    | Description
|:---------------------------------- |:-----------
| COLLECT( [ DISTINCT ] value)       | Returns a multiset of the values
| COUNT( [ DISTINCT ] value [, value]* ) | Returns the number of input rows for which *value* is not null (wholly not null if *value* is composite)
| COUNT(*)                           | Returns the number of input rows
| AVG( [ DISTINCT ] numeric)         | Returns the average (arithmetic mean) of *numeric* across all input values
| SUM( [ DISTINCT ] numeric)         | Returns the sum of *numeric* across all input values
| MAX( [ DISTINCT ] value)           | Returns the maximum value of *value* across all input values
| MIN( [ DISTINCT ] value)           | Returns the minimum value of *value* across all input values
| STDDEV_POP( [ DISTINCT ] numeric)  | Returns the population standard deviation of *numeric* across all input values
| STDDEV_SAMP( [ DISTINCT ] numeric) | Returns the sample standard deviation of *numeric* across all input values
| VAR_POP( [ DISTINCT ] value)       | Returns the population variance (square of the population standard deviation) of *numeric* across all input values
| VAR_SAMP( [ DISTINCT ] numeric)    | Returns the sample variance (square of the sample standard deviation) of *numeric* across all input values
| COVAR_POP(numeric1, numeric2)      | Returns the population covariance of the pair (*numeric1*, *numeric2*) across all input values
| COVAR_SAMP(numeric1, numeric2)     | Returns the sample covariance of the pair (*numeric1*, *numeric2*) across all input values
| REGR_SXX(numeric1, numeric2)       | Returns the sum of squares of the dependent expression in a linear regression model
| REGR_SYY(numeric1, numeric2)       | Returns the sum of squares of the independent expression in a linear regression model

Not implemented:

* REGR_AVGX(numeric1, numeric2)
* REGR_AVGY(numeric1, numeric2)
* REGR_COUNT(numeric1, numeric2)
* REGR_INTERCEPT(numeric1, numeric2)
* REGR_R2(numeric1, numeric2)
* REGR_SLOPE(numeric1, numeric2)
* REGR_SXY(numeric1, numeric2)

### Window functions

| Operator syntax                           | Description
|:----------------------------------------- |:-----------
| COUNT(value [, value ]* ) OVER window     | Returns the number of rows in *window* for which *value* is not null (wholly not null if *value* is composite)
| COUNT(*) OVER window                      | Returns the number of rows in *window*
| AVG(numeric) OVER window                  | Returns the average (arithmetic mean) of *numeric* across all values in *window*
| SUM(numeric) OVER window                  | Returns the sum of *numeric* across all values in *window*
| MAX(value) OVER window                    | Returns the maximum value of *value* across all values in *window*
| MIN(value) OVER window                    | Returns the minimum value of *value* across all values in *window*
| RANK() OVER window                        | Returns the rank of the current row with gaps; same as ROW_NUMBER of its first peer
| DENSE_RANK() OVER window                  | Returns the rank of the current row without gaps; this function counts peer groups
| ROW_NUMBER() OVER window                  | Returns the number of the current row within its partition, counting from 1
| FIRST_VALUE(value) OVER window            | Returns *value* evaluated at the row that is the first row of the window frame
| LAST_VALUE(value) OVER window             | Returns *value* evaluated at the row that is the last row of the window frame
| LEAD(value, offset, default) OVER window  | Returns *value* evaluated at the row that is *offset* rows after the current row within the partition; if there is no such row, instead returns *default*. Both *offset* and *default* are evaluated with respect to the current row. If omitted, *offset* defaults to 1 and *default* to NULL
| LAG(value, offset, default) OVER window   | Returns *value* evaluated at the row that is *offset* rows before the current row within the partition; if there is no such row, instead returns *default*. Both *offset* and *default* are evaluated with respect to the current row. If omitted, *offset* defaults to 1 and *default* to NULL
| NTILE(value) OVER window                  | Returns an integer ranging from 1 to *value*, dividing the partition as equally as possible

Not implemented:

* COUNT(DISTINCT value) OVER window
* FIRST_VALUE(value) IGNORE NULLS OVER window
* LAST_VALUE(value) IGNORE NULLS OVER window
* PERCENT_RANK(value) OVER window
* CUME_DIST(value) OVER window
* NTH_VALUE(value, nth) OVER window

### Grouping functions

| Operator syntax      | Description
|:-------------------- |:-----------
| GROUPING(expression) | Returns 1 if expression is rolled up in the current row's grouping set, 0 otherwise
| GROUP_ID()           | Returns an integer that uniquely identifies the combination of grouping keys
| GROUPING_ID(expression [, expression ] * ) | Returns a bit vector of the given grouping expressions

### User-defined functions

Calcite is extensible. You can define each kind of function using user code.
For each kind of function there are often several ways to define a function,
varying from convenient to efficient.

To implement a *scalar function*, there are 3 options:

* Create a class with a public static `eval` method,
  and register the class;
* Create a class with a public non-static `eval` method,
  and a public constructor with no arguments,
  and register the class;
* Create a class with one or more public static methods,
  and register each class/method combination.

To implement an *aggregate function*, there are 2 options:

* Create a class with public static `init`, `add` and `result` methods,
  and register the class;
* Create a class with public non-static `init`, `add` and `result` methods,
  and a  public constructor with no arguments,
  and register the class.

Optionally, add a public `merge` method to the class; this allows Calcite to
generate code that merges sub-totals.

Optionally, make your class implement the
[SqlSplittableAggFunction]({{ site.apiRoot }}/org/apache/calcite/sql/SqlSplittableAggFunction.html)
interface; this allows Calcite to decompose the function across several stages
of aggregation, roll up from summary tables, and push it through joins.

To implement a *table function*, there are 3 options:

* Create a class with a static `eval` method that returns
  [ScannableTable]({{ site.apiRoot }}/org/apache/calcite/schema/ScannableTable.html)
  or
  [QueryableTable]({{ site.apiRoot }}/org/apache/calcite/schema/QueryableTable.html),
  and register the class;
* Create a class with a non-static `eval` method that returns
  [ScannableTable]({{ site.apiRoot }}/org/apache/calcite/schema/ScannableTable.html)
  or
  [QueryableTable]({{ site.apiRoot }}/org/apache/calcite/schema/QueryableTable.html),
  and register the class;
* Create a class with one or more public static methods that return
  [ScannableTable]({{ site.apiRoot }}/org/apache/calcite/schema/ScannableTable.html)
  or
  [QueryableTable]({{ site.apiRoot }}/org/apache/calcite/schema/QueryableTable.html),
  and register each class/method combination.

To implement a *table macro*, there are 3 options:

* Create a class with a static `eval` method that returns
  [TranslatableTable]({{ site.apiRoot }}/org/apache/calcite/schema/TranslatableTable.html),
  and register the class;
* Create a class with a non-static `eval` method that returns
  [TranslatableTable]({{ site.apiRoot }}/org/apache/calcite/schema/TranslatableTable.html),
  and register the class;
* Create a class with one or more public static methods that return
  [TranslatableTable]({{ site.apiRoot }}/org/apache/calcite/schema/TranslatableTable.html),
  and register each class/method combination.

Calcite deduces the parameter types and result type of a function from the
parameter and return types of the Java method that implements it. Further, you
can specify the name and optionality of each parameter using the
[Parameter]({{ site.apiRoot }}/org/apache/calcite/linq4j/function/Parameter.html)
annotation.

### Calling functions with named and optional parameters

Usually when you call a function, you need to specify all of its parameters,
in order. But that can be a problem if a function has a lot of parameters,
and especially if you want to add more parameters over time.

To solve this problem, the SQL standard allows you to pass parameters by name,
and to define parameters which are optional (that is, have a default value
that is used if they are not specified).

Suppose you have a function `f`, declared as in the following pseudo syntax:

```FUNCTION f(
  INTEGER a,
  INTEGER b DEFAULT NULL,
  INTEGER c,
  INTEGER d DEFAULT NULL,
  INTEGER e DEFAULT NULL) RETURNS INTEGER```

All of the function's parameters have names, and parameters `b`, `d` and `e`
have a default value of `NULL` and are therefore optional.
(In Calcite, `NULL` is the only allowable default value for optional parameters;
this may change
[in future](https://issues.apache.org/jira/browse/CALCITE-947).)

When calling a function with optional parameters,
you can omit optional arguments at the end of the list, or use the `DEFAULT`
keyword for any optional arguments.
Here are some examples:

* `f(1, 2, 3, 4, 5)` provides a value to each parameter, in order;
* `f(1, 2, 3, 4)` omits `e`, which gets its default value, `NULL`;
* `f(1, DEFAULT, 3)` omits `d` and `e`,
  and specifies to use the default value of `b`;
* `f(1, DEFAULT, 3, DEFAULT, DEFAULT)` has the same effect as the previous
  example;
* `f(1, 2)` is not legal, because `c` is not optional;
* `f(1, 2, DEFAULT, 4)` is not legal, because `c` is not optional.

You can specify arguments by name using the `=>` syntax.
If one argument is named, they all must be.
Arguments may be in any other, but must not specify any argument more than once,
and you need to provide a value for every parameter which is not optional.
Here are some examples:

* `f(c => 3, d => 1, a => 0)` is equivalent to `f(0, NULL, 3, 1, NULL)`;
* `f(c => 3, d => 1)` is not legal, because you have not specified a value for
  `a` and `a` is not optional.

