MySQL选择查询具有多个条件 [英] MySQL select query with multiple conditions

问题描述

我写了一个MySQL查询，但是它似乎没有用，因为结果为空.我的代码有什么错误吗?

I have written a MySQL query but it doesn't seem to be working, because the result is empty. Is there any mistake in my code?

$result = mysql_query(
     "SELECT user_id 
      FROM wp_usermeta 
      WHERE 
         (meta_key = 'first_name' AND meta_value = '$us_name') AND         
         (meta_key = 'yearofpassing' AND meta_value = '$us_yearselect') AND 
         (meta_key = 'u_city' AND meta_value = '$us_reg') AND 
         (meta_key = 'us_course' AND meta_value = '$us_course')"
);

推荐答案

我将使用以下查询:

SELECT
  user_id
FROM
  wp_usermeta 
WHERE 
  (meta_key = 'first_name' AND meta_value = '$us_name') OR 
  (meta_key = 'yearofpassing' AND meta_value = '$us_yearselect') OR 
  (meta_key = 'u_city' AND meta_value = '$us_reg') OR
  (meta_key = 'us_course' AND meta_value = '$us_course')
GROUP BY
  user_id
HAVING
  COUNT(DISTINCT meta_key)=4

这将选择满足所有四个条件的所有user_id.

this will select all user_id that meets all four conditions.

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