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
请留意红色部分
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
)
复制代码
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
)
复制代码
执行上面的语句会现在的mysql中会提示:
执行报错:1093 - You can't specify target table 'student' for update in FROM clause 原因是:更新数据时使用了查询,而查询的数据又做了更新的条件,mysql不支持这种方式。 怎么规避这个问题? 再加一层封装,如下:
DELETE
FROM
people
WHERE
peopleName IN (
SELECT
peopleName
FROM(
SELECT
peopleName
FROM
people
GROUP BY
peopleName
HAVING
count(peopleName) > 1
) a
)
AND peopleId NOT IN (
SELECT
peopleName
FROM(
SELECT
min(peopleId)
FROM
people
GROUP BY
peopleName
HAVING
count(peopleName) > 1
) b
)
复制代码
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
)
复制代码
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
)
复制代码
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
)
复制代码
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%'
复制代码
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'
复制代码
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 tableName
SET key = value WHERE key1 IN (
SELECT key1 FROM vitae GROUP BY peopleId)
复制代码
「真诚赞赏,手留余香」
真诚赞赏,手留余香
使用微信扫描二维码完成支付
转载请注明:首页 > 投稿 » mysql去重复删除重复记录(MYSQL 删除重复的数据方法)
继续浏览有关编程的文章
发表评论
版权声明
求资源网所发布的一切破解补丁,软件,以及其他分析文章仅限用于学习和研究目的;不得将上述内容用于商业或者非法用途。
否则,一切后果请用户自负。本站信息来自网络,版权争议与本站无关。您必须在下载后的24个小时之内,从您的电脑中彻底删除上述内容。如果您喜欢该程序,请支持正版软件,购买注册,得到更好的正版服务。如有侵权请邮件与我们联系处理。