MySQL中删除重复数据只保留一条

时间:2022-09-22 22:50:46

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

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MySQL中删除重复数据只保留一条