An expression is a combination of one or more values, operators, and SQL functions that evaluates to a value. An expression generally assumes the data type of its components.
Note:The combined values of the
NLS_SORTsettings determine the rules by which characters are sorted and compared. If
NLS_COMPis set to
LINGUISTICfor your database, then all entities in this chapter will be interpreted according to the rules specified by the
NLS_COMPis not set to
LINGUISTIC, then the functions are interpreted without regard to the
NLS_SORTcan be explicitly set. If it is not set explicitly, it is derived from
NLS_LANGUAGE. Refer to Oracle Database Globalization Support Guide for more information on these settings.
This simple expression evaluates to 4 and has data type
NUMBER (the same data type as its components):
The following expression is an example of a more complex expression that uses both functions and operators. The expression adds seven days to the current date, removes the time component from the sum, and converts the result to
CHAR data type:
You can use expressions in:
The select list of the
A condition of the
WHERE clause and
VALUES clause of the
SET clause of the
For example, you could use an expression in place of the quoted string
'Smith' in this
SET last_name = 'Smith';
SET clause has the expression
last_name) instead of the quoted string '
SET last_name = INITCAP(last_name);
Expressions have several forms, as shown in the following syntax:
Oracle Database does not accept all forms of expressions in all parts of all SQL statements. Refer to the individual SQL statements in Chapter 10 through Chapter 19 for information on restrictions on the expressions in that statement.
You must use appropriate expression notation whenever
expr appears in conditions, SQL functions, or SQL statements in other parts of this reference. The sections that follow describe and provide examples of the various forms of expressions.