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MySQL MAKE_SET()函数在位的值为1且第一个字符串为NULL时返回空值。以下示例将展示这个概念−

示例

mysql> Select MAKE_SET(1, NULL,'A','B');
+---------------------------+
| MAKE_SET(1, NULL,'A','B') |
+---------------------------+
|                           |
+---------------------------+
1 row in set (0.00 sec)