EXPERT RESPONSE
The assignment operator is simply the way PL/SQL sets the value of one
variable to a given value. There is only one assignment operator, := . I'm
not sure where you saw the others listed or used, but they are invalid.
Assignment operators are different from a regular equal sign, =, in that
they are used to assign a specified value to a PL/SQL variable. For
instance, if I wanted to give a variable named V_TEMPERATURE an initial
value of 98.6, I'd use the following assignment statement:
set serveroutput on
DECLARE
v_temperature number := 98.6 ;
BEGIN
dbms_output.put_line('The temperature is ' || v_temperature) ;
END ;
/
I could also change the value of v_temperature in the body of my code as
well:
set serveroutput on
DECLARE
v_temperature number := 98.6 ;
BEGIN
dbms_output.put_line('The initial temperature is ' || v_temperature) ;
v_temperature := 100.6 ;
dbms_output.put_line('The next temperature is ' || v_temperature) ;
v_temperature := v_temperature - 4 ;
dbms_output.put_line('The last temperature is ' || v_temperature) ;
END ;
/
Assigning a value is different from just using the equal sign. Whenever you
see an = in PL/SQL, it is typically used for comparison purposes:
set serveroutput on
DECLARE
v_temperature number := 98.6 ;
BEGIN
IF v_temperature = 99 THEN
dbms_output.put_line('You have a slight fever.')
END IF ;
END ;
/
Notice how the = is used to compare the value of v_temperature (which is
98.6) to the value 99.
That's the key way to differentiate. If you want to compare a value use an
equal sign, but if you want to assign a value to a variable, use the :=
assignment operator.
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