SQL query duplicate record, delete duplicate record method

Source: Internet
Author: User
Tags repetition

Find records for all repeating headings:
SELECT * from T_info a WHERE ((SELECT COUNT (*) from t_info where Title = A.title) > 1) ORDER by Title DESC
One.find a repeating recordRecorded
1. Find all duplicate records
SELECT * FROM table Where repeating field in (Select repeating field from table Group by repeating field having Count (*) >1)
2. Filter duplicate records (show only one bar)
SELECT * from Hzt Where ID in (the Select Max (ID) from Hzt Group by Title)
Note: The ID maximum one record is shown here
two. Delete duplicate records
1. Delete all duplicate records (with caution)
Delete table Where repeating field in (Select repeating field from table Group by repeating field having Count (*) >1)
2. Keep One (this should be what most people need ^_^)
Delete hzt Where ID not in (the Select Max (ID) from Hzt Group by Title)
Note: The maximum one record for the ID is retained here
1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determine
SELECT * from People
where Peopleid in (select Peopleid from People GROUP by Peopleid have count (Peopleid) > 1)

2, delete redundant records in the table, duplicate records are based on a single field (Peopleid) to judge, leaving only the smallest ROWID records
Delete from people
where Peopleid in (select Peopleid from People GROUP by Peopleid have count (Peopleid) > 1)
and rowID not in (select min (rowid) from people GROUP by Peopleid have Count (Peopleid) >1)

3. Find redundant duplicate records (multiple fields) in the table
SELECT * FROM Vitae a
where (A.PEOPLEID,A.SEQ) in (select Peopleid,seq from Vitae GROUP by PEOPLEID,SEQ have count (*) > 1)

4. Delete extra duplicate records (multiple fields) in the table, leaving only the record with ROWID minimum
Delete from Vitae a
where (A.PEOPLEID,A.SEQ) in (select Peopleid,seq from Vitae GROUP by PEOPLEID,SEQ have count (*) > 1)
and rowID not in (select min (rowid) from Vitae GROUP by PEOPLEID,SEQ have Count (*) >1)

5. Find redundant duplicate records (multiple fields) in the table, not including the smallest ROWID records
SELECT * FROM Vitae a
where (A.PEOPLEID,A.SEQ) in (select Peopleid,seq from Vitae GROUP by PEOPLEID,SEQ have count (*) > 1)
and rowID not in (select min (rowid) from Vitae GROUP by PEOPLEID,SEQ have Count (*) >1)
Add:
There are more than two duplicate records, one is a completely duplicate record, that is, all the fields are duplicated records, and the second is some key field duplicate records, such as the Name field is repeated, and the other fields may not be repeated or repeated can be ignored.
1, for the first kind of repetition, easier to solve, using
SELECT DISTINCT * from TableName
You can get a result set with no duplicate records.

If the table needs to delete duplicate records (duplicate records retain 1), you can delete them as follows
SELECT DISTINCT * to #Tmp from TableName
drop table TableName
SELECT * Into TableName from #Tmp
drop table #Tmp

This duplication occurs because the table is poorly designed and the unique index columns are added to resolve.
2, this kind of repetition problem usually requires to keep the first record in the duplicate record, the operation method is as follows
Suppose there is a duplicate field name,address, which requires the result set to be unique for both fields
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 on (select Autoid from #tmp2)

SQL query duplicate record, delete duplicate record method

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