|PostgreSQL Reference Manual - Volume 1 - SQL Language Reference|
by The PostgreSQL Global Development Group
Paperback (6"x9"), 716 pages
RRP £32.00 ($49.95)
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2.2 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
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 section 7 Functions and Operators. An example is the
We have already discussed constants in section 2.1.2 Constants. The following sections discuss the remaining options.
|ISBN 0954612027||PostgreSQL Reference Manual - Volume 1 - SQL Language Reference||See the print edition|