合并 2 个 SQL 语句

Question

我需要组合以下 2 个 SELECT 语句，以便第二个语句的结果作为第一个 select 的每一行中的一列出现。

SELECT MEM.Id,
   EN.artistName,
   EN.dateAdded,
   EN.voteStatus,
   ES.enterNextRound,
   ES.notified,
   ES.voted,
   GR.genre,
   ES.entrantId AS bandID
FROM recMembers AS MEM
LEFT JOIN recEntrantStatus AS ES
   ON MEM.Id = ES.judgeId
LEFT JOIN recEntrants AS EN
   ON ES.entrantId = EN.Id
LEFT JOIN recGenre AS GR
   ON EN.genreId = GR.Id
WHERE MEM.Id = @memberId
   AND ES.roundId = 2

SELECT COUNT(enterNextRound) 
FROM recEntrantStatus
WHERE enterNextRound = 1
  AND roundId = 2
  AND entrantId = ES.entrantId

其中“ES.entrantId”取自第一个选择中访问的当前行。

Answer 1

您可以使用

OUTER APPLY

：

SELECT MEM.Id, 
  EN.artistName, 
  EN.dateAdded, 
  EN.voteStatus, 
  ES.enterNextRound,
  ES.notified, 
  ES.voted, 
  GR.genre, 
  ES.entrantId AS bandID, 
  src.CountEnterNextRound
FROM recMembers AS MEM
LEFT JOIN recEntrantStatus AS ES
  ON MEM.Id = ES.judgeId
LEFT JOIN recEntrants AS EN
  ON ES.entrantId = EN.Id
LEFT JOIN recGenre AS GR
  ON EN.genreId = GR.Id
OUTER APPLY
(
  SELECT COUNT(enterNextRound) CountEnterNextRound
  FROM recEntrantStatus
  WHERE enterNextRound = 1
    AND roundId = 2
    AND entrantId = @memberId
) src
WHERE MEM.Id = @memberId
  AND ES.roundId = 2

根据您的编辑，您是否尝试过：

SELECT MEM.Id,
   EN.artistName,
   EN.dateAdded,
   EN.voteStatus,
   ES.enterNextRound,
   ES.notified,
   ES.voted,
   GR.genre,
   ES.entrantId AS bandID,
   (SELECT COUNT(enterNextRound) 
    FROM recEntrantStatus
    WHERE enterNextRound = 1
      AND roundId = 2
      AND entrantId = ES.entrantId) CountEnterNextRound
FROM recMembers AS MEM
LEFT JOIN recEntrantStatus AS ES
   ON MEM.Id = ES.judgeId
LEFT JOIN recEntrants AS EN
   ON ES.entrantId = EN.Id
LEFT JOIN recGenre AS GR
   ON EN.genreId = GR.Id
WHERE MEM.Id = @memberId
   AND ES.roundId = 2

甚至：

SELECT MEM.Id,
   EN.artistName,
   EN.dateAdded,
   EN.voteStatus,
   ES.enterNextRound,
   ES.notified,
   ES.voted,
   GR.genre,
   ES.entrantId AS bandID,
   src.CountEnterNextRound
FROM recMembers AS MEM
LEFT JOIN recEntrantStatus AS ES
   ON MEM.Id = ES.judgeId
LEFT JOIN recEntrants AS EN
   ON ES.entrantId = EN.Id
LEFT JOIN recGenre AS GR
   ON EN.genreId = GR.Id
LEFT JOIN
(
  SELECT COUNT(enterNextRound) CountEnterNextRound, entrantId
  FROM recEntrantStatus
  WHERE enterNextRound = 1
      AND roundId = 2
  GROUP BY entrantId
) src
  ON ES.entrantId = src.entrantId
WHERE MEM.Id = @memberId
   AND ES.roundId = 2;

Answer 2

将其包装在子查询中并使用

CROSS JOIN

SELECT MEM.Id,
        EN.artistName,
        EN.dateAdded,
        EN.voteStatus,
        ES.enterNextRound,
        ES.notified,
        ES.voted,
        GR.genre,
        ES.entrantId AS bandID,
        s.totalCount
FROM recMembers AS MEM
        LEFT JOIN recEntrantStatus AS ES
                ON MEM.Id = ES.judgeId
        LEFT JOIN recEntrants AS EN
                ON ES.entrantId = EN.Id
        LEFT JOIN recGenre AS GR
                ON EN.genreId = GR.Id
        CROSS JOIN (
                SELECT COUNT(enterNextRound) totalCount
                FROM recEntrantStatus
                WHERE enterNextRound = 1
                        AND roundId = 2
                        AND entrantId = @memberId
                ) s
WHERE MEM.Id = @memberId
        AND ES.roundId = 2

Answer 3

怎么样

SELECT * 
FROM
(
    SELECT MEM.Id, EN.artistName, EN.dateAdded, EN.voteStatus, ES.enterNextRound,
    ES.notified, ES.voted, GR.genre, ES.entrantId AS bandID
    FROM recMembers AS MEM
    LEFT JOIN recEntrantStatus AS ES
    ON MEM.Id = ES.judgeId
    LEFT JOIN recEntrants AS EN
    ON ES.entrantId = EN.Id
    LEFT JOIN recGenre AS GR
    ON EN.genreId = GR.Id
    WHERE MEM.Id = @memberId
    AND ES.roundId = 2
) x
,
(
    SELECT COUNT(enterNextRound) as Total
    FROM recEntrantStatus
    WHERE enterNextRound = 1
    AND roundId = 2
    AND entrantId = @memberId
) y

当您在没有连接的情况下执行 FROM 2 个表时，您会得到像交叉连接一样的笛卡尔积。所以应该是相同的执行时间。

这是隐式的写法。