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What is the difference between = and: = assignment operators?
Actually, they both are assignment operator and used to assign values but the significant difference between them is as follows −
= operator assigns a value either as a part of the SET statement or as a part of the SET clause in an UPDATE statement, in any other case = operator is interpreted as a comparison operator. On the other hand, := operator assigns a value and it is never interpreted as a comparison operator.
mysql> Update estimated_cost1 SET Tender_value = '8570.000' where id = 2; Query OK, 1 row affected (0.06 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> Update estimated_cost1 SET Tender_value := '8575.000' where id = 2; Query OK, 1 row affected (0.06 sec) Rows matched: 1 Changed: 1 Warnings: 0
In the above two queries, we have used the = operator as well as: = operator to UPDATE the value of the table.
mysql> Set @A = 100; Query OK, 0 rows affected (0.01 sec) mysql> Select @A; +------+ | @A | +------+ | 100 | +------+ 1 row in set (0.00 sec) mysql> Set @B := 100; Query OK, 0 rows affected (0.00 sec) mysql> Select @B; +------+ | @B | +------+ | 100 | +------+ 1 row in set (0.00 sec)
In the above two queries, we used = operator and: = operator to assign a value to a user variable. We can see that in both the situations = operator and: = operator have the same usage and functionality. But in the following query = operator, works as a comparison operator and give the result as ‘TRUE’ i.e. both the user variables @A and @B are having same values.
mysql> Select @A = @B; +---------+ | @A = @B | +---------+ | 1 | +---------+ 1 row in set (0.00 sec)
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