4.2. 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). Value expressions are therefore also called scalar expressions (or even simply expressions). The expression syntax allows the calculation of values from primitive parts using arithmetic, logical, set, and other operations.

A value expression is one of the following:

• A constant or literal value.

• A column reference.

• A positional parameter reference, in the body of a function definition or prepared statement.

• A subscripted expression.

• A field selection expression.

• An operator invocation.

• A function call.

• An aggregate expression.

• A type cast.

• A scalar subquery.

• An array constructor.

• A row constructor.

• Another value expression in parentheses, useful to group subexpressions and override precedence.

In addition to this list, there are a number of constructs that can be classified as an expression but do not follow any general syntax rules. These generally have the semantics of a function or operator and are explained in the appropriate location in