Value expressions

Value expressions are used in a variety of contexts, such as in the target list of the SELECT command, as new column values in INSERT or UPDATE, or in search conditions in a number of commands. The result of a value expression is sometimes called a scalar, to distinguish it from the result of a table expression (which is a table).

Aggregate expressions

An aggregate expression represents the application of an aggregate function across the rows selected by a query.

The supported syntax of an aggregate expression is one of the following:

aggregate_name (expression [ , ... ] [ order_by_clause ] ) [ FILTER ( WHERE filter_clause ) ]
aggregate_name (DISTINCT expression [ , ... ]) [ FILTER ( WHERE filter_clause ) ]
aggregate_name ( * ) [ FILTER ( WHERE filter_clause ) ]

where aggregate_name is one of the aggregation functions listed on Aggregate functions, and expression is a value expression that does not contain an aggregate expression or a window function call.

DISTINCT cannot be used with an ORDER BY clause in RisingWave.

Row constructors

A row constructor is an expression that builds a row value using values from its member fields.

ROW([expression][,...])

Example

The following two statements create a table and add values to the table.

CREATE TABLE t (v1 int, v2 int);
INSERT INTO t VALUES (1,12), (2,13), (3,30);

The row constructor in the statement below returns all rows in table t in the form of row values (,).

SELECT row (v1, v2*2) AS demo FROM t;

  demo  
--------
 (1,24)
 (2,26)
 (3,60)
(3 rows)

Array constructors

An array constructor is an expression that creates an array from a group of values.

An array can be construcuted with the following syntax.

ARRAY [expression1, expression2, ...]

For example:

SELECT ARRAY[1, 2, 3*4];
----------
 {1,2,12}
(1 row)

An array constructor can be nested in another array constructor. For example:

SELECT ARRAY[ARRAY[1, 2], ARRAY[3, 4]];
----------
 {{1,2},{3,4}}
(1 row)

For a nested array constructor, ARRAY cannot be omitted. The following statement cannot be parsed.

SELECT ARRAY[[1,2], [3,4]];

When you create a table, define an array with square brackets. For example:

CREATE TABLE (f1 INT[], f2 INT[]);

INSERT INTO arr VALUES (ARRAY[1,2], ARRAY[3,4]);