sql query to find duplicate records in column

SQL non-repeating lookup statistics2007-06-29 11:04The example table is as follows:Table Name: MYTESTTID COL1 COL2 COL31 1 A A2 1 A A3 2 A A4 2 B A5 3 b b6 3 b b7 4 C B8 4 C B9 1 A A2 B A1. Find a field in the table and repeat for only one:SELECT DISTINCT COL1 from MYTEST;The result is:12342. Find multiple fields in a table where a field is not duplicated:SELECT * from MYTEST WHERE rowid in (SELECT min (rowid) from MYTEST GROUP by COL1);The result is:

follows: The code is as follows Copy Code mysql> desc test1; +--------------+------------------+------+-----+---------+----------------+| Field | Type | Null | Key | Default | Extra |+--------------+------------------+------+-----+---------+----------------+| ID | int (a) unsigned | NO | PRI | NULL | auto_increment || SenderName | varchar (32) | YES | | NULL | || Receivername | VARCHAR (64) | YES | | NULL | || SENDER | VARCHAR (64) | NO | | NULL | || RECEIVER | VARC

This article describes three SQL queries for repeating records and deleting duplicate records , and each uses different methods to illustrate other roles and possibilities, as well as its efficiency. SELECT *, COUNT (distinct name) from table group by name Results: ID Name count (distinct name)1 a 12 B 13 C

Label: 1, duplicate records in the lookup table are judged by a single field (Peopleid) .Select*From people where Peopleidinch(SelectPeopleid from People GROUP by Peopleid have Count (Peopleid)>1) 2, delete redundant records in the table, repeat records are based on a single field (Peopleid) to judge, leaving only rowi

SQL Multiple primary key tables, when the inserted data is duplicated, are prompted to violate the primary KEY constraint that cannot be inserted by the error. So, how do I find duplicate values for the inserted data? Workaround: Use Group bySuppose there is a table #a , there are saleid,vendorid,comid,price,saleprice,quantity and other fields. The primary key is: Saleid,vendorid,comid three of them. Assu

) from vitae group by peopleid, seq having count (*)> 1)5. Search for redundant duplicate records (multiple fields) in the table, excluding records with the smallest rowidSelect * From vitaeWhere (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, s

= @idFetch cur_rows into @id, @maxEndClose Cur_rowsSET ROWCOUNT 0Method TwoThere are two meanings of duplicate records, one is a completely duplicate record, that is, all fields are duplicated records, and the second is some key field duplicate

Label:Database UserInfo Delete duplicate user name delete duplicate username phone number the same user name phone number only one user is reserved 01. Querying duplicate data based on multiple fields With Data1 as ( Select Mobilephone,name from UserInfoGROUP BY Mobilephone,nameHaving Count (*) >1 ), 02. Duplicate Da

Select A.name as table name, b.name as column name, c.name as type, b.max_length as Byte count, b.precision As Integer, B.scale as decimal from Sys.tables a INNER JOIN Sys.columns B on a.object_id=b.object_id inner join Sys. Types C on c.user_type_id=b.user_type_idThis article is from the "IT" blog, so be sure to keep this source http://8577754.blog.51cto.com/8567754/1553205How to use a statement in an SQL

[Name],subject,score Here for a good understanding only one column to get the following results With the example of the language accomplishment line train, it is easy to add the other two columns, Select [Name],Chinese =caseWhen subject= ' language ' then score else 0EndMathematics =caseWhen subject= ' math ' then score else 0EndForeign Language =caseWhen subject= ' foreign language ' then score else 0EndFrom StudentscoreGroup BY [Name],subject,scor

1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determineSelect * from people where inch (Select from Group by having Count >1)2, delete redundant records in the table, duplicate

The instance resolution and SQL horizontal display are displayed in the row-to-column manner of SQL query statements. This article shares two examples of horizontal display of rows and columns in SQL query statements for your refe

vitae 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) Supplement: There are more than two duplicate records. One is a completely repeated record, that is, record with all fields already exists. The other is record with

Friends of the novel station, now the daily collection of articles will have a lot of repeated articles. So we put forward the need to go heavy.The Chaptername of the Jieqi_article_chapter table for this CMS system is not indexed, and the first step is to build the index. Note: It is risky to build an index, please do a backup of the data first. SQL as follows, replace the article ID 1 at the time of use:SELECT DISTINCT (A.chapterid), a.articleid,a.ch

Usage scenarios:For example, you need to query all student numbers with scores greater than 95, separated by commas into a string, from the Student score table.To prepare the test data:CREATE TABLE score (ID int,score int)INSERT into score values (1,90)INSERT into score values (2,96)INSERT into score values (3,99)It is now necessary to query the result string "2,,3" with a single statement.The

SQL Single or group de-duplication Query methodThe following data are used for testing:Table Name: T_demo Id Name Project Grade 1 Xiao ming Mathematical 59 1 Xiao ming Chinese 59 1 Xiao ming English 59 2 Little Red Mathematical 100 2 Little Red

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 GROUP BY account_instance_id, follow_account_ins

In most applications, it is common to return a large number of qualified records. The most typical method is to search. In the search application, the user gives the search criteria and the server finds the matching records. However, a search usually returns a large amount of data records. If you are on a webpage, the page is usually implemented by pagination. Th

'the value of the Key5' fromheadertable awhereA.headerid= 10000 SELECTA.*, t.a0001 as 'the value of the Key1', t.a0002 as 'the value of the Key2', t.a0003 as 'the value of the Key3', t.a0004 as 'the value of the Key4', t.a0005 as 'the value of the Key5' fromHeadertable AInner Join (SelectHeaderid, Detailkey, detailvalues fromdetailtable) T Pivot (MAX(detailvalues) forDetailkeyinch(a0001,a0002,a0003,a0004,a0005)) T onT.headerid=A.headeridwhereA.headerid= 10000 　　

Today I received a task with a student information table (Excel table) containing more than 10 thousand records. Now I want to import this table to the database and set the student ID as the primary key, but now the student ID in this table has repeated records. I must first find these repeated records and then filter them. After research, the problem is finally