how to find duplicate rows in sql

Method One: Use in the programming of T-SQLAssign a column number, sort by col1,col2 combination, delete database duplicate rows (duplicate data), keep only one row//Col1,col2 is the database columnDelete a from (select Col1,col2,row_number () over (partition by col1,col2 ORDER by COL1) as RN from DATABASE) a where a.rn >1 method Two: Use in the ETL select distan

Original article: http://support.microsoft.com/kb/139444/SummaryThe Microsoft SQL Server table should not contain duplicate rows and non-unique primary keys. For the sake of conciseness, we sometimes refer to the primary key as "key" or "Pk" in this article, but this always indicates "primary key ". Repeated PK violates entity integrity and is not allowed in the

. We'll use the Common Table Expression (CTE) and put the ' self ' Join query in it.With duplicates as (select distinct A.custid as customer_id from Customers2 a join customers2 B on A.custid Let ' s check which rows got deleted.SELECT * from Customers2 goScenario 2.b:delete all duplicate records but keep the first original oneLet ' s first truncate the CUSTOMERS2 table and add the same

SQL Delete duplicate rows (all or distinct)/*Delete a duplicate row SELECT statement Use the all or distinct option to display all rows in the table that meet the criteria, or delete duplicate

First the code, you can see the SQL statement to remove duplicate records, get duplicate records Copy Code code as follows: ALTER procedure [dbo]. [Proc_itemmaster_getunique] @PAGEINDEX int, @uid int, @itemnumber varchar (50) As Begin Tran--Start a transaction drop table [Itemmaster]. [dbo]. [Testim]--delete table --Transfer the record to

Tags: sql StackOverflow de-weightproblemSuppose you have a table with a larger amount of data (for example, 300,000+ rows), where there are duplicate rows (other than the primary key, the other column data is the same), how do you quickly go heavy? My watch looks like this.MyTable-----------RowID int not null identity(

Mysql complex SQL statements (query and delete duplicate rows), mysqlsql 1. Find duplicate rows SELECT * FROM blog_user_relation a WHERE (a.account_instance_id,a.follow_account_instance_id) IN (SELECT account_instance_id,follow_account_instance_id FROM blog_user_relation GRO

SQL Server deduplication is one of our most common actions, and here's a look at six different ways SQL Server can remove duplicate rows for your reference.1. If there is an ID field, it is a unique fielddelect table TableName where ID not in (the Select Max (ID) from the table group by Col1,col2,col3:. )The field foll

For repeated row deletion problems, it is difficult to find a suitable answer on the Internet and there are a lot of questions, but there is no solution to the previous record in the search engine. In fact, this problem can be effectively solved. 1. If the table does not have a primary key (or the same row does not have different content columns), you need to create an auto-increment column to distinguish different columns. For example Copy codeThe Code is as follows: alter table [tablename]

For repeated row deletion problems, it is difficult to find a suitable answer on the Internet and there are a lot of questions, but there is no solution to the previous record in the search engine.In fact, this problem can be effectively solved.1. If the table does not have a primary key (or the same row does not have different content columns), you need to create an auto-increment column to distinguish different columns. For exampleCopy codeThe Code is as follows:Alter table [tablename] add [TI

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 tabelSelect * 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 tablenameDelete tablenameGoInsert tablename select * from # temp SqlclubGoDrop table # temp The prece

Tags: target div Delete sel not int nbsp article is your1. If there is an ID field, it is a unique fieldDelect 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 you use to judge the repetition, such as only col1, so that the record is the same as long as the col1 field has the same contents.2, if you are judging all fields, you can do the same.SELECT * into #aa from table group by Id1,id2,....Delete TableINSER

Recently, I have been sorting out the database of my website. The database is mysql. Because of the increasing access function, I imported access and reviewed the SQL. There are a lot of data, 0.15 million records, about 1 GB. The two fields a and B of some data are repeated, so that duplicate rows can be considered as duplicated data, as long as any row is retai

In a table, some fields are not primary keys and are not unique, but in the process of use, the field does not apply duplicates, and sometimes it repeats. So, to find the row for a repeating field, use the SQL statement:--That is:--select * from table Where repeating field in (Select repeating field from table Group by repeating field having Count (*) >1)--to a specific example Select * from T_exte RM where Mainkeyindex in (select Mainkeyindex from T_

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 tableInsert

Where has count (*) >1 GROUP BY Col1,col2,col3,col4 ) The field followed by the GROUP BY clause is the condition that you use to determine the repetition, such as only col1, so as long as the content of the Col1 field is the same as that of the record. 5. Copy Code code 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 has count (*) >1 GROUP by col1,col2,col3 ...) 6.

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Tags: blog http sp c log r AD BSWith such a problem, a SQL statement is used to query the names of students who have more than 80 points per course.Here is the tableAnalysis, query each course is more than 80 students. SELECT DISTINCT name from dbo.student WHERE fenshuStatements less than or equal to 80 select name from Dbo.student WHERE fenshuThis is repeated, and it is worthwhile to use the words in the not-in (no-time) statement to spell the two se

You have a try1 I want to abroad1 Those are good Men1 We are good MenThe content after the 2nd character of each line is not checked, so I am tank root I love tank is the same. Delete a row in a large data file where some fields are duplicated A recently written data acquisition program generated a file containing more than 10 million rows of data, the data consists of 4 fields, according to the requirements need to delete the second field

by Field 1, Field 2, Field 3 having COUNT (*) > 1) Where: Field 1, Field 2, Field 3 refers to the three fields that need to establish a unique constraint, selfid refers to one of the self-increment fields in tables table. 2. Delete duplicate records and keep only the Selfid minimum records, that is, the first inserted records:[SQL]View Plaincopy DELETE from dbo. Tablesign WHERE S