Share six ways for SQL Server to delete duplicate rows

1. If an ID field exists, it is a unique field. Copy codeThe Code is as follows: delect table where id not in (
Select max (id) from table group by col1, col2, col3...
)

The field followed by the group by clause is the condition for you to judge repetition. For example, if only col1 is used, if the content of col1 is the same, the record is the same.

2. This can also be used to determine all fields.Copy codeThe Code is as follows: select * into # aa from table group by id1, id2 ,....
Delete table
Insert into table
Select * from # aa

3. No IDCopy codeThe Code is as follows: select identity (int, 1, 1) as id, * into # temp from tabel
Delect # where id not in (
Select max (id) from # group by col1, col2, col3 ...)
Delect table
Inset into table (...)
Select... from # temp

4. col1 + ',' + col2 + ','... col5 join primary keyCopy codeThe Code is as follows: select * from table where col1 + ',' + col2 + ','... col5 in (
Select max (col1 + ',' + col2 + ','... col5) from table
Where having count (*)> 1
Group by col1, col2, col3, col4
)

The field followed by the group by clause is the condition for you to judge repetition. For example, if only col1 is used, if the content of col1 is the same, the record is the same.

5.Copy codeThe Code is as follows: select identity (int, 1, 1) as id, * into # temp from tabel
Select * from # temp where id in (
Select max (id) from # emp where having count (*)> 1 group by col1, col2, col3 ...)

6.Copy codeThe Code is as follows: select distinct * into # temp from tablename
Delete tablename
Go
Insert tablename select * from # temp Sqlclub
Go
Drop table # temp

The preceding describes how SQL Server deletes duplicate rows.