用SQL语句,删除掉重复项只保留一条
在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢
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
peopleName IN (
SELECT
peopleName
FROM
people
GROUP BY
peopleName
HAVING
count(peopleName) > 1
)
AND peopleId NOT IN (
SELECT
min(peopleId)
FROM
people
GROUP BY
peopleName
HAVING
count(peopleName) > 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
)
6.消除一个字段的左边的第一位：
UPDATE tableName
SET [ Title ]= RIGHT ([ Title ],(len([ Title ]) - 1))
WHERE
Title LIKE ‘村%‘
7.消除一个字段的右边的第一位：
UPDATE tableName
SET [ Title ]= LEFT ([ Title ],(len([ Title ]) - 1))
WHERE
Title LIKE ‘%村‘
8.假删除表中多余的重复记录（多个字段），不包含rowid最小的记录
UPDATE vitae
SET ispass =- 1
WHERE
peopleId IN (
SELECT
peopleId
FROM
vitae
GROUP BY
peopleId
原文：https://www.cnblogs.com/mracale/p/9146260.html