Syntax

left_expr = right_expr

Description

Equal operator. Evaluates both SQL expressions and returns 1 if they are equal, 0 if they are not equal, or NULL if either expression is NULL. If the expressions return different data types (for example, a number and a string), a type conversion is performed.

When used in row comparisons these two queries are synonymous and return the same results:

SELECT (t1.a, t1.b) = (t2.x, t2.y) FROM t1 INNER JOIN t2;

SELECT (t1.a = t2.x) AND (t1.b = t2.y) FROM t1 INNER JOIN t2;

To perform a NULL-safe comparison, use the <=> operator.

= can also be used as an assignment operator.

Examples

SELECT 1 = 0;
+-------+
| 1 = 0 |
+-------+
|     0 |
+-------+

SELECT '0' = 0;
+---------+
| '0' = 0 |
+---------+
|       1 |
+---------+

SELECT '0.0' = 0;
+-----------+
| '0.0' = 0 |
+-----------+
|         1 |
+-----------+

SELECT '0.01' = 0;
+------------+
| '0.01' = 0 |
+------------+
|          0 |
+------------+

SELECT '.01' = 0.01;
+--------------+
| '.01' = 0.01 |
+--------------+
|            1 |
+--------------+

SELECT (5 * 2) = CONCAT('1', '0');
+----------------------------+
| (5 * 2) = CONCAT('1', '0') |
+----------------------------+
|                          1 |
+----------------------------+

SELECT 1 = NULL;
+----------+
| 1 = NULL |
+----------+
|     NULL |
+----------+

SELECT NULL = NULL;
+-------------+
| NULL = NULL |
+-------------+
|        NULL |
+-------------+