|Oracle® Database PL/SQL User's Guide and Reference
10g Release 2 (10.2)
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An assignment statement sets the current value of a variable, field, parameter, or element. The statement consists of an assignment target followed by the assignment operator and an expression. When the statement is executed, the expression is evaluated and the resulting value is stored in the target. For more information, see "Assigning Values to Variables".
assignment statement ::=
An attribute of an object type. The name must be unique within the object type (but can be reused in other object types). You cannot initialize an attribute in its declaration using the assignment operator or
DEFAULT clause. Also, you cannot impose the
NULL constraint on an attribute.
A nested table, index-by table, or varray previously declared within the current scope.
A PL/SQL cursor variable previously declared within the current scope. Only the value of another cursor variable can be assigned to a cursor variable.
A combination of variables, constants, literals, operators, and function calls. The simplest expression consists of a single variable. For the syntax of
expression, see "Expression Definition". When the assignment statement is executed, the expression is evaluated and the resulting value is stored in the assignment target. The value and target must have compatible datatypes.
A field in a user-defined or
A cursor variable declared in a PL/SQL host environment and passed to PL/SQL as a bind variable. The datatype of the host cursor variable is compatible with the return type of any PL/SQL cursor variable. Host variables must be prefixed with a colon.
A variable declared in a PL/SQL host environment and passed to PL/SQL as a bind variable. Host variables must be prefixed with a colon.
A numeric expression that must return a value of type
BINARY_INTEGER, or a value implicitly convertible to that datatype.
An indicator variable declared in a PL/SQL host environment and passed to PL/SQL. Indicator variables must be prefixed with a colon. An indicator variable indicates the value or condition of its associated host variable. For example, in the Oracle Precompiler environment, indicator variables let you detect nulls or truncated values in output host variables.
An instance of an object type previously declared within the current scope.
OUT parameter of the subprogram in which the assignment statement appears.
A user-defined or
%ROWTYPE record previously declared within the current scope.
A PL/SQL variable previously declared within the current scope.
By default, unless a variable is initialized in its declaration, it is initialized to
NULL every time a block or subprogram is entered. Always assign a value to a variable before using that variable in an expression.
You cannot assign nulls to a variable defined as
NULL. If you try, PL/SQL raises the predefined exception
VALUE_ERROR. Only the values
NULL can be assigned to a Boolean variable. You can assign the result of a comparison or other test to a Boolean variable.
You can assign the value of an expression to a specific field in a record. You can assign values to all fields in a record at once. PL/SQL allows aggregate assignment between entire records if their declarations refer to the same cursor or table. Example 1-2, "Assigning Values to Variables With the Assignment Operator" shows how to copy values from all the fields of one record to another:
You can assign the value of an expression to a specific element in a collection, by subscripting the collection name.
Example 13-1 illustrates various ways to declare and then assign values to variables.
DECLARE wages NUMBER; hours_worked NUMBER := 40; hourly_salary CONSTANT NUMBER := 17.50; -- constant value does not change country VARCHAR2(64) := 'UNKNOWN'; unknown BOOLEAN; TYPE comm_tab IS TABLE OF NUMBER INDEX BY PLS_INTEGER; commissions comm_tab; TYPE jobs_var IS VARRAY(10) OF employees.job_id%TYPE; jobids jobs_var; CURSOR c1 IS SELECT department_id FROM departments; -- cursor declaration deptid departments.department_id%TYPE; emp_rec employees%ROWTYPE; -- do not need TYPE declaration in this case BEGIN /* the following are examples of assignment statements */ wages := hours_worked * hourly_salary; -- compute wages country := UPPER('italy'); unknown := (country = 'UNKNOWN'); commissions(5) := 20000 * 0.15; commissions(8) := 20000 * 0.18; jobids := jobs_var('ST_CLERK'); jobids.EXTEND(1); jobids(2) := 'SH_CLERK'; OPEN c1; FETCH c1 INTO deptid; CLOSE c1; emp_rec.department_id := deptid; emp_rec.job_id := jobids(2); END; /
For examples, see the following: