tsql - T-SQL 发现差异

Question

我找到了 Jeff Smith 的解决方案，它显示了两个表之间的差异：

SELECT MIN(TableName) as TableName, ID, COL1, COL2, COL3 ...
FROM
(
  SELECT 'Table A' as TableName, A.ID, A.COL1, A.COL2, A.COL3, ...
  FROM A
  UNION ALL
  SELECT 'Table B' as TableName, B.ID, B.COL1, B.COl2, B.COL3, ...
  FROM B
) tmp
GROUP BY ID, COL1, COL2, COL3 ...
HAVING COUNT(*) = 1
ORDER BY ID

在我的项目中，我需要比较例如。仅 col1 和 col2，rest 用于其他操作。我试着用

HAVING (COUNT(col1) = 1 and COUNT(col2) = 1)

但没有效果。

您能否为我提供解决方案？

score 3 · Accepted Answer

获取使用 EXCEPT中不存在的COL1和COL2in的值：AB

SELECT COL1, COL2 FROM A
EXCEPT
SELECT COL1, COL2 FROM B

将结果用作派生表将它们连接回A并获取所有列：

SELECT 'A' AS SRC, A.COL1, A.COL2, A.COL3...
FROM (
  SELECT COL1, COL2 FROM A
  EXCEPT
  SELECT COL1, COL2 FROM B
) AS diff
INNER JOIN A ON diff.COL1 = A.COL1 AND diff.COL2 = A.COL2

类似地，使用 EXCEPT 获取仅存在于中的COL1和的值，并加入结果集以获取相应的完整行。COL2BB

将这两组与 UNION ALL 结合起来：

SELECT 'A' AS SRC, A.COL1, A.COL2, A.COL3...
FROM (
  SELECT COL1, COL2 FROM A
  EXCEPT
  SELECT COL1, COL2 FROM B
) AS diff
INNER JOIN A ON diff.COL1 = A.COL1 AND diff.COL2 = A.COL2

UNION ALL

SELECT 'B' AS SRC, B.COL1, B.COL2, B.COL3...
FROM (
  SELECT COL1, COL2 FROM B
  EXCEPT
  SELECT COL1, COL2 FROM A
) AS diff
INNER JOIN B ON diff.COL1 = B.COL1 AND diff.COL2 = B.COL2
;

score 0 · Accepted Answer

您正在从错误的位置删除列。您应该将其从列列表中删除，而不是从星号中删除：

SELECT MIN(TableName) as TableName, ID, COL1, COL2
FROM
(
  SELECT 'Table A' as TableName, A.ID, A.COL1, A.COL2
  FROM A
  UNION ALL
  SELECT 'Table B' as TableName, B.ID, B.COL1, B.COl2
  FROM B
) tmp
GROUP BY ID, COL1, COL2
HAVING COUNT(*) = 1
ORDER BY ID

要保留结果中的其他列，您可以使用MIN（或朋友）保留它们：

SELECT MIN(TableName) as TableName, ID, COL1, COL2, MIN(COL3), MIN(COL4), ...
FROM
(
  SELECT 'Table A' as TableName, A.ID, A.COL1, A.COL2, A.COL3, A.COL4, ...
  FROM A
  UNION ALL
  SELECT 'Table B' as TableName, B.ID, B.COL1, B.COL2, B.COL3, B.COL4, ...
  FROM B
) tmp
GROUP BY ID, COL1, COL2
HAVING COUNT(*) = 1
ORDER BY ID

请注意，这在某些情况下效果不佳。如果两个表中的两行相同（包括 ID），那么即使不是，它也会发现它是不同的。此外，在这个版本中，如果您有多个相同的行COL1，COL2那么这也不能很好地工作。我会将这两个表连接在一起以进行更可靠的比较。

tsql - T-SQL 发现差异

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