自连接查询以查找重复记录

Question

我有一个大约有 32 列的 table，我想检查重复的行，但是有两列是唯一的，因此每一行都不同。所以我需要 JOIN 条件基本上是自我加入重复记录，其中除了两列之外所有列都相等。

Answer 1

要查找重复的行，查询将是（col1...col30 将排除每行始终唯一的两列）

SELECT
  col1,
  col2,
  ...,
  col30
FROM
  your_table
GROUP BY
  col1,
  col2,
  ...,
  col30
HAVING
  COUNT(*)>1

编辑：从您要删除重复行的备注中可以看出。假设您有每行唯一的列 id1 和 id2（即主键）和可以重复的列 col1..col4。以下面的脚本为例，删除重复行：

CREATE TABLE #tt(
    id1 INT,
    id2 INT,
    col1 INT,
    col2 INT,
    col3 INT,
    col4 INT,
    PRIMARY KEY(id1,id2)
);

INSERT INTO #tt(id1,id2,col1,col2,col3,col4)
VALUES (1,1,1,1,1,1),
       (1,2,1,1,1,1),
       (1,3,1,1,1,1),
       (2,1,1,1,1,1),
       (3,1,2,2,2,2),
       (4,1,2,2,2,2),
       (2,2,2,2,2,2),
       (3,3,3,3,3,3),
       (4,2,3,3,3,3);

DELETE
    t
FROM
    #tt AS t
    INNER JOIN (
        SELECT
            id1,
            id2,
            ROW_NUMBER() OVER (PARTITION BY col1,col2,col3,col4 ORDER BY id1,id2) AS rn
        FROM
            #tt
    ) AS trn ON
        trn.id1=t.id1 AND
        trn.id2=t.id2
WHERE
    trn.rn>1;

SELECT*FROM #tt;

DROP TABLE #tt;

Answer 2

你也可以这样使用：

SELECT *
FROM yourTable t
WHERE 1 < (
    SELECT COUNT(*) 
    FROM yourTable ti
    WHERE t.uniqueCol1 = ti.uniqueCol1 AND t.uniqueCol2 = ti.uniqueCol2
    GROUP BY nonUniqueCol1, nonUniqueCol2, ..., nonUniqueColn)

或者只过滤重复行而不显示原始行，您可以使用：

SELECT *
FROM (SELECT *,
          ROW_NUMBER() OVER (PARTITION BY nonUniqueCol1, nonUniqueCol2, ..., nonUniqueColn
                             ORDER BY uniqueCol1, uniqueCol2) As seq
      FROM yourTable) t
WHERE (seq > 1)

自连接查询以查找重复记录

Self Join query to find duplicate records

sql

sql-server

sql-server-2008-r2