What is the difference between = and := assignment operators?

Actually, they are both assignment operators, used to assign values, but the significant differences between them are as follows-

= operator assignment is Part of a SET statement or as part of the SET clause in an UPDATE statement, and in any other case the = operator is interpreted as a comparison operator. On the other hand, the := operator assigns a value and 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 used the = operator and the := operator to update the table values.

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 use = operator and := operator to assign values ​​to user variables. We can see that = operator and := operator have the same usage and functionality in both cases. But in the following query = operator is used as comparison operator and gives the result as "TRUE" i.e. user variables @A and @B have the same value.

mysql> Select @A = @B;
+---------+
| @A = @B |
+---------+
|       1 |
+---------+
1 row in set (0.00 sec)

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