You can also assign a value to a user variable in statements other than SET : User Defined Variables « Select Query « MySQL Tutorial

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MySQL Tutorial » Select Query » User Defined Variables

2. 22. 2. 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 = is treated as a comparison operator in non-SET statements:


mysql>

mysql> SET @t1=0, @t2=1, @t3=2;

Query OK, 0 rows affected (0.00 sec)



mysql>

mysql> SELECT @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3;

+----------------------+------+------+------+

| @t1:=(@t2:=1)+@t3:=4 | @t1  | @t2  | @t3  |

+----------------------+------+------+------+

|                    5 | 5    | 1    | 4    |

+----------------------+------+------+------+

1 row in set (0.00 sec)



mysql>

2. 22. User Defined Variables
	2. 22. 1.	User variables are written as @var_name.
	2. 22. 2.	You can also assign a value to a user variable in statements other than SET
	2. 22. 3.	Using User-Defined Variables
	2. 22. 4.	Use user-defined variable in the where statement
	2. 22. 5.	Create dynamic sql command

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