mysql - mysql 计数显示比预期更多的结果

Question

这是我的查询：

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON active.AGENTUID = mls.MSTLISTBRD
    AND mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing';

表格很大，所以很难显示表格结构。

当我在没有 的情况下运行计数时AND mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing'，我得到了预期的结果（大约 500）。但是当我想用这些参数过滤时，它会返回 25000+ 个结果，而它应该低于 500。

我认为这是一个语法问题，但查找类似的问题，我无法提出解决方案。

Answer 1

使用WHERE子句

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON active.AGENTUID = mls.MSTLISTBRD
    WHERE mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing';

Answer 2

SELECT COUNT(*) 
  FROM jos_mls mls 
  JOIN jos_activeagents active 
    ON active.AGENTUID = mls.MSTLISTBRD
   AND (mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing');

或者

SELECT COUNT(*) 
  FROM jos_mls mls 
  JOIN jos_activeagents active 
    ON active.AGENTUID = mls.MSTLISTBRD
   AND mls.MSTACTSTA IN('Active','Keep Showing');

Answer 3

AND具有优先权，OR因此您应该在条件的第二部分周围使用括号来获得所需的输出：

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON active.AGENTUID = mls.MSTLISTBRD
    AND (mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing');

您获得的行数比预期多得多的原因是您运行的实际查询与此相同：

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON (active.AGENTUID = mls.MSTLISTBRD
    AND mls.MSTACTSTA = 'Active') OR mls.MSTACTSTA = 'Keep Showing';