What is the difference between = and := in MySQL?

0

Issue

What is the difference in between

set test_var = 20;

and

set test_var:=20;

as they both seem to assign the value ?

Solution

Both of them are assignment operators but one thing I can find their differences is that = can be used to perform boolean operation while := cannot.

valid: SUM(val = 0)
Invalid: SUM(val := 0)

FROM User-Defined Variables

One more thing, You can also assign a value to a user variable in statements other than SET. In this case, the assignment operator must be := and not = because the latter is treated as the comparison operator = in non-SET statements.

mysql> SET @t1=1, @t2=2, @t3:=4;
mysql> SELECT @t1, @t2, @t3, @t4 := @t1+@t2+@t3;
+------+------+------+--------------------+
| @t1  | @t2  | @t3  | @t4 := @t1+@t2+@t3 |
+------+------+------+--------------------+
|    1 |    2 |    4 |                  7 | 
+------+------+------+--------------------+

Answered By – John Woo

This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0

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