MySQL - 对 SELECT 结果进行 UNION

Question

我的表中有很多行，我准备 test_result_table:

SELECT * FROM 
(
  SELECT ID, DATA
  FROM table
  WHERE DATA = "A" OR DATA = "B" OR DATA = "C"
) AS test_result_table

我该如何做到这一点:

SELECT * FROM
    (
        SELECT 1 AS RESULT, ID 
        FROM test_result_table
        WHERE DATA = "A"
      UNION  
        SELECT 2 AS RESULT, ID 
        FROM test_result_table
        WHERE DATA = "B"
      UNION
        SELECT 3 AS RESULT, ID 
        FROM test_result_table
        WHERE DATA = "C"
    ) AS result_id
ORDER BY RESULT

我知道与临时表有关，有更好(更快)的解决方案吗？

我期望(x =某个ID):

RESULT |ID
1      |x
1      |x 
2      |x
2      |x
3      |x

Answer 1

使用函数 FIND_IN_SET() 可以获得相同的结果这将返回列的值RESULT:

SELECT t.*
FROM (
  SELECT 
    FIND_IN_SET(DATA, 'A,B,C') AS RESULT, 
    ID
  FROM tablename
) t
WHERE t.RESULT > 0
ORDER BY t.RESULT

查看简化版 demo .
我无法判断它的效率，但它肯定更简单。