Scalar Expressions - CockroachDB

Most SQL statements can contain scalar expressions that compute new values from data. For example, in the query SELECT ceil(price) FROM items, the expression ceil(price) computes the rounded-up value of the values from the price column. Scalar expressions produce values suitable to store in a single table cell (one column of one row). They can be contrasted with and , which produce results structured as a table. The following sections describe how to construct scalar expressions.

Constants

Constant expressions represent a simple value that doesn’t change. They are described further in section .

Column references

An expression in a query can refer to columns in the current data source in two ways:

The name of the column, e.g., price in SELECT price FROM items.
- If the name of a column is also a , the name must be appropriately quoted. For example: SELECT "Default" FROM configuration.
- If the name is ambiguous (e.g., when joining across multiple tables), it is possible to disambiguate by prefixing the column name by the table name. For example, SELECT items.price FROM items.
The ordinal position of the column. For example, SELECT @1 FROM items selects the first column in items.

This is a CockroachDB SQL extension.

Use ordinal references with care in production code. During schema updates, column ordinal positions can change and invalidate existing queries that use ordinal positions based on a previous version of the schema.

Unary and binary operations

An expression prefixed by a unary operator, or two expressions separated by a binary operator, form a new expression. For a full list of CockroachDB operators, with details about their order of precedence and which data types are valid operands for each operator, see .

Value comparisons

The standard operators < (less than), > (greater than), <= (less than or equal to), >= (greater than or equal to), = (equals), <> and != (not equal to), IS (identical to), and IS NOT (not identical to) can be applied to any pair of values from a single data type, as well as some pairs of values from different data types. See also . The following special rules apply:

NULL is always ordered smaller than every other value, even itself.
NULL is never equal to anything via =, even NULL. To check whether a value is NULL, use the IS operator or the conditional expression IFNULL(...).

Typing rule

All comparisons accept any combination of argument types and result in type BOOL.

Comparison with `NaN`

CockroachDB recognizes the special value NaN (Not-a-Number) for scalars of type or . As per the IEEE 754 standard, NaN is considered to be different from every other numeric value in comparisons. There are two exceptions however, made for compatibility with PostgreSQL:

NaN is considered to be equal with itself in comparisons. IEEE 754 specifies that NaN is different from itself.
NaN is considered to be less than every other value, including -INFINITY. IEEE 754 specifies that NaN does not order with any other value, i.e., x <= NaN and x >= NaN are both false for every value of x including infinities.

These exceptions exist so that the value NaN can be used in WHERE clauses and indexes. For example:

> SELECT FLOAT 'NaN' < 1, 1 < FLOAT 'NaN', FLOAT 'NaN' < FLOAT 'NaN';

  ?column? | ?column? | ?column?
-----------+----------+-----------
    true   |  false   |  false
(1 row)

> SELECT FLOAT 'NaN' = FLOAT 'NaN' AS result;

  result
----------
   true
(1 row)

> SELECT FLOAT 'NaN' < FLOAT '-INFINITY' AS result;

  result
----------
   true
(1 row)

Multi-valued comparisons

Syntax:

<expr> <comparison> ANY <expr>
<expr> <comparison> SOME <expr>
<expr> <comparison> ALL <expr>

The value comparison operators <, >, =, <=, >=, <> and !=, as well as the pattern matching operators [NOT] LIKE and [NOT] ILIKE, can be applied to compare a single value on the left to multiple values on the right. This is done by combining the operator using the keywords ANY/SOME or ALL. The right operand can be either an array, a tuple or . The result of the comparison is true if and only if:

For ANY / SOME, the comparison of the left value is true for any element on the right.
For ALL, the comparison of the left value is true for every element on the right.

For example:

> SELECT 12 = ANY (10, 12, 13);

  ?column?
------------
    true
(1 row)

> SELECT 12 = ALL (10, 12, 13);

  ?column?
------------
   false
(1 row)

> SELECT 1 = ANY ARRAY[2, 3, 1];

  ?column?
------------
    true
(1 row)

Typing rule

The comparison between the type on the left and the element type of the right operand must be possible.

Set membership

Syntax:

<expr> IN <expr>
<expr> IN ( ... subquery ... )

<expr> NOT IN <expr>
<expr> NOT IN ( ... subquery ... )

Returns TRUE if and only if the value of the left operand is part of the result of evaluating the right operand. In the subquery form, any can be used. For example:

> SELECT a IN (1, 2, 3) FROM sometable;

> SELECT a IN (SELECT * FROM allowedvalues) FROM sometable;

> SELECT ('x', 123) IN (SELECT * FROM rows);

See for more details and performance best practices.

Typing rule

IN requires its right operand to be a homogeneous tuple type and its left operand to match the tuple element type. The result has type BOOL.

String pattern matching

Syntax:

<expr> LIKE <expr>
<expr> ILIKE <expr>
<expr> NOT LIKE <expr>
<expr> NOT ILIKE <expr>

Evaluates both expressions as strings, then tests whether the string on the left matches the pattern given on the right. Returns TRUE if a match is found or FALSE otherwise, or the inverted value for the NOT variants. Patterns can contain _ to match any single character, or % to match any sequence of zero or more characters. ILIKE causes the match to be tested case-insensitively. For example:

> SELECT 'monday' LIKE '%day' AS a, 'tuesday' LIKE 'tue_day' AS b, 'wednesday' ILIKE 'W%' AS c;

   a   |  b   |  c
-------+------+-------
  true | true | true
(1 row)

Typing rule

The operands must be either both STRING or both BYTES. The result has type BOOL.

String matching using POSIX regular expressions

Syntax:

<expr> ~ <expr>
<expr> ~* <expr>
<expr> !~ <expr>
<expr> !~* <expr>

Evaluates both expressions as strings, then tests whether the string on the left matches the pattern given on the right. Returns TRUE if a match is found or FALSE otherwise, or the inverted value for the ! variants. The variants with an asterisk * use case-insensitive matching; otherwise the matching is case-sensitive. The pattern is expressed using POSIX regular expression syntax. Unlike LIKE patterns, a regular expression is allowed to match anywhere inside a string, not only at the beginning. For example:

> SELECT 'monday' ~ 'onday' AS a, 'tuEsday' ~ 't[uU][eE]sday' AS b, 'wednesday' ~* 'W.*y' AS c;

   a   |  b   |  c
-------+------+-------
  true | true | true
(1 row)

Typing rule

The operands must be either both STRING or both BYTES. The result has type BOOL.

String matching using SQL regular expressions

Syntax:

<expr> SIMILAR TO <expr>
<expr> NOT SIMILAR TO <expr>

Evaluates both expressions as strings, then tests whether the string on the left matches the pattern given on the right. Returns TRUE if a match is found or FALSE otherwise, or the inverted value for the NOT variant. The pattern is expressed using the SQL standard’s definition of a regular expression. This is a mix of SQL LIKE patterns and POSIX regular expressions:

_ and % denote any character or any string, respectively.
. matches specifically the period character, unlike in POSIX where it is a wildcard.
Most of the other POSIX syntax applies as usual.
The pattern matches the entire string (as in LIKE, unlike POSIX regular expressions).

For example:

> SELECT 'monday' SIMILAR TO '_onday' AS a, 'tuEsday' SIMILAR TO 't[uU][eE]sday' AS b, 'wednesday' SIMILAR TO 'w%y' AS c;

   a   |  b   |  c
-------+------+-------
  true | true | true
(1 row)

Typing rule

The operands must be either both STRING or both BYTES. The result has type BOOL.

Function calls and SQL special forms

General syntax:

<name> ( <arguments...> )

A built-in function name followed by an opening parenthesis, followed by a comma-separated list of expressions, followed by a closing parenthesis. This applies the named function to the arguments between parentheses. When the function’s namespace is not prefixed, the determine which function is called. See also . In addition, the following SQL special forms are also supported:

Special form	Equivalent to
`AT TIME ZONE`	`timezone()`
`CURRENT\_CATALOG`	`current\_catalog()`
`COLLATION FOR`	`pg\_collation\_for()`
`CURRENT\_DATE`	`current\_date()`
`CURRENT\_ROLE`	`current\_user()`
`CURRENT\_SCHEMA`	`current\_schema()`
`CURRENT\_TIMESTAMP`	`current\_timestamp()`
`CURRENT\_TIME`	`current\_time()`
`CURRENT\_USER`	`current\_user()`
`EXTRACT( FROM )`	`extract("", )`
`EXTRACT\_DURATION( FROM )`	`extract\_duration("", )`
`OVERLAY( PLACING FROM FOR )`	`overlay(, , , )`
`OVERLAY( PLACING FROM )`	`overlay(, , )`
`POSITION( IN )`	`strpos(, )`
`SESSION\_USER`	`current\_user()`
`SUBSTRING( FOR FROM )`	`substring(, , )`
`SUBSTRING( FOR )`	`substring(, 1, )`
`SUBSTRING( FROM FOR )`	`substring(, , )`
`SUBSTRING( FROM )`	`substring(, )`
`TRIM( FROM )`	`btrim(, )`
`TRIM(, )`	`btrim(, )`
`TRIM(FROM )`	`btrim()`
`TRIM(LEADING FROM )`	`ltrim(, )`
`TRIM(LEADING FROM )`	`ltrim()`
`TRIM(TRAILING FROM )`	`rtrim(, )`
`TRIM(TRAILING FROM )`	`rtrim()`
`USER`	`current\_user()`

Typing rule

In general, a function call requires the arguments to be of the types accepted by the function, and returns a value of the type determined by the function. However, the typing of function calls is complicated by the fact SQL supports function overloading. See Revisiting SQL Typing in CockroachDB for more details.

Subscripted expressions

You can use the [… ] operator to access one item in an or value. For example:

If the name a refers to an ARRAY of 10 values, a[3] will retrieve the third value. ARRAY values use 1-based indexing, so the first value has index 1.
If the name j refers to a JSONB array of 10 values, j[3] will retrieve the fourth value. JSONB arrays use zero-based indexing, so the first value has index 0.
If the name j refers to a JSON object {"a": {"b":1}}, then j['a'] will access key a and retrieve {"b":1}. j['a']['b'] will access key b and retrieve 1.

The result of the subscripted expression is NULL if:

The index is smaller than or equal to 0, or larger than the size of the array.
The key or key path does not exist in the JSON object.

Typing rule

The subscripted expression must have an array type; the index expression must have type INT. The result has the element type of the subscripted expression.

Conditional expressions

Expressions can test a conditional expression and, depending on whether or which condition is satisfied, evaluate to one or more additional operands. These expression formats share the following property: some of their operands are only evaluated if a condition is true. This matters especially when an operand would be invalid otherwise. For example, IF(a=0, 0, x/a) returns 0 if a is 0, and x/a otherwise.

`IF` expressions

Syntax:

IF ( <cond>, <expr1>, <expr2> )

Evaluates <cond, then evaluates <expr1 if the condition is true, or <expr2 otherwise. In most cases, the expression corresponding to the case when the condition is false is not evaluated. The exception is when the expression is a subquery, which is eagerly evaluated when execution of the query begins.

Typing rule

The condition must have type BOOL, and the two remaining expressions must have the same type. The result has the same type as the expression that was evaluated.

Simple `CASE` expressions

Syntax:

CASE <cond>
  WHEN <condval1> THEN <expr1>
  [ WHEN <condvalx> THEN <exprx> ] ...
  [ ELSE <expr2> ]
END

Evaluates <cond, then picks the WHEN branch where <condval is equal to <cond, then evaluates and returns the corresponding THEN expression. If no WHEN branch matches, the ELSE expression is evaluated and returned, if any. Otherwise, NULL is returned. In most cases, conditions and result expressions after the first match are not evaluated. The exception is subqueries, which are eagerly evaluated when execution of the query begins.

Typing rule

The condition and the WHEN expressions must have the same type. The THEN expressions and the ELSE expression, if any, must have the same type. The result has the same type as the THEN/ELSE expressions.

Searched `CASE` expressions

Syntax:

CASE WHEN <cond1> THEN <expr1>
   [ WHEN <cond2> THEN <expr2> ] ...
   [ ELSE <expr> ]
END

In order, evaluates each <cond expression; at the first <cond expression that evaluates to TRUE, returns the result of evaluating the corresponding THEN expression. If none of the <cond expressions evaluates to true, then evaluates and returns the value of the ELSE expression, if any, or NULL otherwise. In most cases, conditions and result expressions after the first match are not evaluated. The exception is subqueries, which are eagerly evaluated when execution of the query begins.

Typing rule

All the WHEN expressions must have type BOOL. The THEN expressions and the ELSE expression, if any, must have the same type. The result has the same type as the THEN/ELSE expressions.

`NULLIF` expressions

Syntax:

NULLIF ( <expr1>, <expr2> )

Equivalent to: IF ( <expr1> = <expr2>, NULL, <expr1> )

Typing rule

Both operands must have the same type, which is also the type of the result.

`COALESCE` and `IFNULL` expressions

Syntax:

IFNULL ( <expr1>, <expr2> )
COALESCE ( <expr1> [, <expr2> [, <expr3> ] ...] )

COALESCE evaluates the first expression first. If its value is not NULL, its value is returned directly. Otherwise, it returns the result of applying COALESCE on the remaining expressions. If all the expressions are NULL, NULL is returned. In most cases, arguments to the right of the first non-null argument are not evaluated. The exception is subqueries, which are eagerly evaluated when execution of the query begins. IFNULL(a, b) is equivalent to COALESCE(a, b).

Typing rule

The operands must have the same type, which is also the type of the result.

Logical operators

The Boolean operators AND, OR and NOT are available. Syntax:

NOT <expr>
<expr1> AND <expr2>
<expr1> OR <expr2>

AND and OR are commutative. Moreover, the input to AND and OR is not evaluated in any particular order. Some operand may not even be evaluated at all if the result can be fully ascertained using only the other operand.

This is different from the left-to-right “short-circuit logic” found in other programming languages. When it is essential to force evaluation order, use a conditional expression.

Typing rule

The operands must have type BOOL. The result has type BOOL.

Aggregate expressions

An aggregate expression has the same syntax as a function call, with a special case for COUNT:

<name> ( <arguments...> )
COUNT ( * )

The difference between aggregate expressions and function calls is that the former use and can only appear in the list of rendered expressions in a . An aggregate expression computes a combined value, depending on which aggregate function is used, across all the rows currently selected.

Typing rule

The operand and return types are determined like for regular function calls.

Window function calls

A window function call has the syntax of a function call followed by an OVER clause:

<name> ( <arguments...> ) OVER <window>
<name> ( * ) OVER <window>

It represents the application of a window or aggregate function over a subset (“window”) of the rows selected by a query.

Typing rule

The operand and return types are determined like for regular function calls.

Explicit type coercions

Syntax:

<expr> :: <type>
CAST (<expr AS <type>)

Evaluates the expression and converts the resulting value to the specified type. An error is reported if the conversion is invalid. For example: CAST(now() AS DATE) Note that in many cases a type annotation is preferable to a type coercion. See type annotations for more details.

Typing rule

The operand can have any type. The result has the type specified in the CAST expression. As a special case, if the operand is a literal, a constant expression or a placeholder, the CAST type is used to guide the typing of the operand. See Revisiting SQL Typing in CockroachDB for more details.

Collation expressions

Syntax:

<expr> COLLATE <collation>

Evaluates the expression and converts its result to a collated string with the specified collation. For example: 'a' COLLATE de

Typing rule

The operand must have type STRING. The result has type COLLATEDSTRING.

Array constructors

Syntax:

ARRAY[ <expr>, <expr>, ... ]

Evaluates to an array containing the specified values. For example:

> SELECT ARRAY[1,2,3] AS a;

     a
-----------
  {1,2,3}
(1 row)

The data type of the array is inferred from the values of the provided expressions. All the positions in the array must have the same data type. If there are no expressions specified (empty array), or all the values are NULL, then the type of the array must be specified explicitly using a type annotation. For example:

> SELECT ARRAY[]:::int[];

To convert the results of a subquery to an array, use ARRAY(...) instead.

CockroachDB also recognizes the syntax ARRAY(a, b, c) as an alias for ARRAY[a, b, c]. This is an experimental, CockroachDB-specific SQL extension and may be removed in a later version of CockroachDB.

Typing rule

The operands must all have the same type. The result has the array type with the operand type as element type.

Tuple constructors

Syntax:

(<expr, <expr>, ...)
ROW (<expr, <expr>, ...)

Evaluates to a tuple containing the values of the provided expressions. For example:

> SELECT ('x', 123, 12.3) AS a;

       a
----------------
  (x,123,12.3)
(1 row)

The data type of the resulting tuple is inferred from the values. Each position in a tuple can have a distinct data type. CockroachDB supports accessing the Nth element in a tuple as a single table cell using the syntax (...).@N. For example:

> SELECT (t).@2 FROM (SELECT (1,'b',2.3) AS t);

  ?column?
------------
  b
(1 row)

CockroachDB also supports expanding all elements of a tuple as a single row in a table with the (<tuple).* notation. This notation works as the inverse of the tuple-creating notation (.*). For example:

> WITH tuples AS (SELECT (t.*) AS tuple FROM (SELECT 1,'b',2.3) AS t(x,y,z))  -- Build the tuples, with labels
   SELECT (tuple).* FROM tuples;  -- Expands the tuples and restore the column labels

  x | y |  z
----+---+------
  1 | b | 2.3
(1 row)

Typing rule

The operands can have any type. The result has a tuple type whose item types are the types of the operands.

Explicitly typed expressions

Syntax:

<expr>:::<type
ANNOTATE_TYPE(<expr, <type>)

Evaluates to the given expression, requiring the expression to have the given type. If the expression doesn’t have the given type, an error is returned. Type annotations are specially useful to guide the arithmetic on numeric values. For example:

> SELECT (1 / 5):::INT;

ERROR: unsupported binary operator: <int> / <int> (desired <int>)
SQLSTATE: 22023

> SELECT (1 / 5);

         ?column?
--------------------------
  0.20000000000000000000
(1 row)

> SELECT (1 / 5)::INT;
  int8
--------
     0
(1 row)

Type annotations are also different from cast expressions in that they do not cause the value to be converted. For example, now()::DATE converts the current timestamp to a date value (and discards the current time), whereas now():::DATE triggers an error message (that now() does not have type DATE). See Revisiting SQL Typing in CockroachDB for more information about context-dependent typing.

Typing rule

The operand must be implicitly coercible to the given type. The result has the given type.

Subquery expressions

See for more details and performance best practices. You can use any as subquery.

Scalar subqueries

Syntax:

( ... subquery ... )

Evaluates the subquery, asserts that it returns a single row and single column, and then evaluates to the value of that single cell. For example, the following query returns TRUE if there are more rows in table users than in table admins:

> SELECT (SELECT COUNT(*) FROM users) > (SELECT COUNT(*) FROM admins);

Typing rule

The operand must have a table type with only one column. The result has the type of that single column.

Existence test on the result of subqueries

Syntax:

EXISTS ( ... subquery ... )
NOT EXISTS ( ... subquery ... )

Evaluates the subquery and then returns TRUE or FALSE depending on whether the subquery returned any row (for EXISTS) or didn’t return any row (for NOT EXISTS).

Typing rule

The operand can have any table type. The result has type BOOL.

Conversion of subquery results to an array

Syntax:

ARRAY( ... subquery ... )

Evaluates the subquery and converts its results to an array. To convert a list of scalar expressions to an array, use ARRAY[...] instead.

​Constants

​Column references

​Unary and binary operations

​Value comparisons

​Typing rule

​Comparison with NaN

​Multi-valued comparisons

​Typing rule

​Set membership

​Typing rule

​String pattern matching

​Typing rule

​String matching using POSIX regular expressions

​Typing rule

​String matching using SQL regular expressions

​Typing rule

​Function calls and SQL special forms

​Typing rule

​Subscripted expressions

​Typing rule

​Conditional expressions

​IF expressions

​Typing rule

​Simple CASE expressions

​Typing rule

​Searched CASE expressions

​Typing rule

​NULLIF expressions

​Typing rule

​COALESCE and IFNULL expressions

​Typing rule

​Logical operators

​Typing rule

​Aggregate expressions

​Typing rule

​Window function calls

​Typing rule

​Explicit type coercions

​Typing rule

​Collation expressions

​Typing rule

​Array constructors

​Typing rule

​Tuple constructors

​Typing rule

​Explicitly typed expressions

​Typing rule

​Subquery expressions

​Scalar subqueries

​Typing rule

​Existence test on the result of subqueries

​Typing rule

​Conversion of subquery results to an array

​See also

Constants

Column references

Unary and binary operations

Value comparisons

Typing rule

Comparison with `NaN`

Multi-valued comparisons

Typing rule

Set membership

Typing rule

String pattern matching

Typing rule

String matching using POSIX regular expressions

Typing rule

String matching using SQL regular expressions

Typing rule

Function calls and SQL special forms

Typing rule

Subscripted expressions

Typing rule

Conditional expressions

`IF` expressions

Typing rule

Simple `CASE` expressions

Typing rule

Searched `CASE` expressions

Typing rule

`NULLIF` expressions

Typing rule

`COALESCE` and `IFNULL` expressions

Typing rule

Logical operators

Typing rule

Aggregate expressions

Typing rule

Window function calls

Typing rule

Explicit type coercions

Typing rule

Collation expressions

Typing rule

Array constructors

Typing rule

Tuple constructors

Typing rule

Explicitly typed expressions

Typing rule

Subquery expressions

Scalar subqueries

Typing rule

Existence test on the result of subqueries

Typing rule

Conversion of subquery results to an array

See also