MySQL - 真/假查询在两台服务器上返回不同

Question

对此感到困惑。

在两台服务器上运行相同版本的 MySQL。 (从完全相同的 rpm 构建)- 沿线的某个地方，一些开发人员改变了一些东西......

服务器 1:

mysql> select ( not 1 = 2 );

0
1 row in set (0.00 sec)

服务器 2:

mysql> select ( not 1 = 2 );

1
1 row in set (0.00 sec)

两个服务器:

mysql> sHOW VARIABLES LIKE 'version';

| version       | 5.6.12 |

Answer 1

你应该检查 HIGH_NOT_PRECEDENCE运营商。

官方文档指出:

The precedence of the NOT operator is such that expressions such as NOT a BETWEEN b AND c are parsed as NOT (a BETWEEN b AND c). In some older versions of MySQL, the expression was parsed as (NOT a) BETWEEN b AND c. The old higher-precedence behavior can be obtained by enabling the HIGH_NOT_PRECEDENCE SQL mode.

Fiddle 测试此行为 here .

顺便说一句，我建议比较 x != y 而不是使用 not (x = y)。