在 SELECT 语句中将两个子查询合并为一个？

Question

有没有最好的方法用这两个子查询来制作这个 SELECT 语句？

SELECT N.ID, N.NAME 
   (SELECT TR.PUZZLE 
    FROM puzzles TR
    WHERE TR.TEAMID = "152" 
      AND TR.NID= N.ID) AS PUZZLE_OK,
   (SELECT TR.PUZZLE_BIS 
    FROM puzzles TR
    WHERE TR.TEAMID = "152" 
      AND TR.NID= N.ID) AS PUZZLE_BIS_OK
FROM news N
WHERE N.SERIESID = "1"

Answer 1

您可以改用JOIN重写查询：

SELECT N.ID, N.NAME, TR.PUZZLE AS PUZZLE_OK, TR.PUZZLE_BIS AS PUZZLE_BIS_OK
FROM news N
JOIN puzzles TR ON TR.NID = N.ID
WHERE N.SERIESID = "1"
  AND TR.TEAMID = "152"

请注意，如果对于来自news的给定ID值可能不存在puzzles条目，您应该使用LEFT JOIN并将puzzles上的WHERE条件移动到JOIN 。 然后，这将以与您的子查询相同的方式返回PUZZLE_OK和PUZZLE_BIS_OK NULL值：

SELECT N.ID, N.NAME, TR.PUZZLE AS PUZZLE_OK, TR.PUZZLE_BIS AS PUZZLE_BIS_OK
FROM news N
LEFT JOIN puzzles TR ON TR.NID = N.ID AND TR.TEAMID = "152"
WHERE N.SERIESID = "1"

注意我已将news上的别名更改为N以保持SELECT子句与您问题中子查询中的内容一致。