SQL查询和删除重复字段的内容

--例如：
id           NAME         VALUE
1               a                 pp
2               a                 pp
3               b                 iii
4               b                 pp
5               b                 pp
6               c                 pp
7               c                 pp
8               c                 iii
--id是主键
--要求得到这样的结果
id           NAME         VALUE
1               a                 pp
3               b                 iii
4               b                 pp
6               c                 pp
8               c                 iii

--方法1
DELETE YourTable
WHERE  [id] NOT   IN (SELECT MAX([id])
                      FROM   YourTable
                      GROUP BY
                             (NAME + VALUE)) 

--方法2

DELETE a
FROM   表 a
       LEFT   JOIN (
                SELECT id = MIN(id)
                FROM   表
                GROUP BY
                       NAME,
                       VALUE
            )b
            ON  a.id = b.id
WHERE  b.id IS NULL 

--查询及删除重复记录的SQL语句
--查询及删除重复记录的SQL语句
--1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

SELECT *
FROM   people
WHERE  peopleId IN (SELECT peopleId
                    FROM   people
                    GROUP BY
                           peopleId
                    HAVING COUNT(peopleId) > 1)
--2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录

DELETE
FROM   people
WHERE  peopleId IN (SELECT peopleId
                    FROM   people
                    GROUP BY
                           peopleId
                    HAVING COUNT(peopleId) > 1)
       AND rowid NOT IN (SELECT MIN(rowid)
                         FROM   people
                         GROUP BY
                                peopleId
                         HAVING COUNT(peopleId) > 1)
--3、查找表中多余的重复记录（多个字段）

SELECT *
FROM   vitae a
WHERE  (a.peopleId, a.seq) IN (SELECT peopleId,
                                      seq
                               FROM   vitae
                               GROUP BY
                                      peopleId,
                                      seq
                               HAVING COUNT(*) > 1)
--4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

DELETE
FROM   vitae a
WHERE  (a.peopleId, a.seq) IN (SELECT peopleId,
                                      seq
                               FROM   vitae
                               GROUP BY
                                      peopleId,
                                      seq
                               HAVING COUNT(*) > 1)
       AND rowid NOT IN (SELECT MIN(rowid)
                         FROM   vitae
                         GROUP BY
                                peopleId,
                                seq
                         HAVING COUNT(*) > 1)

--5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录

SELECT *
FROM   vitae a
WHERE  (a.peopleId, a.seq) IN (SELECT peopleId,
                                      seq
                               FROM   vitae
                               GROUP BY
                                      peopleId,
                                      seq
                               HAVING COUNT(*) > 1)
       AND rowid NOT IN (SELECT MIN(rowid)
                         FROM   vitae
                         GROUP BY
                                peopleId,
                                seq
                         HAVING COUNT(*) > 1)
--(二)
--比方说
--在A表中存在一个字段“name”，
--而且不同记录之间的“name”值有可能会相同，
--现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；

SELECT NAME,
       COUNT(*)
FROM   A
GROUP BY
       NAME
HAVING COUNT(*) > 1

--如果还查性别也相同大则如下:

SELECT NAME,
       sex,
       COUNT(*)
FROM   A
GROUP BY
       NAME,
       sex
HAVING COUNT(*) > 1(三)
--方法一

DECLARE @max     integer,
        @id      integer

DECLARE cur_rows CURSOR LOCAL
FOR
    SELECT 主字段,
           COUNT(*)
    FROM   表名
    GROUP BY
           主字段
    HAVING COUNT(*) > ； 1

OPEN cur_rows
FETCH cur_rows INTO @id,@max
WHILE @@fetch_status = 0
BEGIN
    SELECT @max = @max -1
    SET ROWCOUNT @max
    DELETE
    FROM   表名
    WHERE  主字段 = @id

    FETCH cur_rows INTO @id,@max
END
CLOSE cur_rows
SET ROWCOUNT 0

--方法二
--＂重复记录＂有两个意义上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。
--1、对于第一种重复，比较容易解决，使用

SELECT DISTINCT *
FROM   tableName
--就可以得到无重复记录的结果集。
--如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除

SELECT DISTINCT * INTO #Tmp
FROM   tableName

DROP TABLE tableName
SELECT * INTO tableName
FROM   #Tmp

DROP TABLE #Tmp
--发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。
--2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下
--假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集
SELECT IDENTITY(INT, 1, 1)  AS autoID,
       * INTO #Tmp
FROM                           tableName

SELECT MIN(autoID) AS autoID INTO #Tmp2
FROM   #Tmp
GROUP BY
       NAME,
       autoID

SELECT *
FROM   #Tmp
WHERE  autoID IN (SELECT autoID
                  FROM   #tmp2)
--最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写在select子句中省去此列）(四)
--查询重复

SELECT *
FROM   tablename
WHERE  id IN (SELECT id
              FROM   tablename
              GROUP BY
                     id
              HAVING COUNT(id) > 1)