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.
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 section devoted to a particular SQL statement in this book 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.