delete duplicate rows in sql

Row Operations of SQL statements: rows of SQL statements SQL statements are explained in the following articles: 1. SQL statement Row Operations 2. SQL statement-based table operations 3. Database Operations for

SQL removes duplicate records, SQL removes duplicates There are two Repeated Records. One is a completely repeated record, that is, records with all fields being repeated, and the other is records with duplicate key fields, such as duplicate Name fields, other fields are not

**************************************** ***Sqlserver2000 Delete duplicate data (Summary)**************************************** ***I. Primary KeyI. Unique field ID (unique primary key) Delete user tableWhere id not in(Select max (ID) from user table group by col1, col2, col3...) The field followed by the group by clause is the condition for you to judge repeti

PHP$DBI=NewDbmysql;$DBI-GT;DBH = ' Mysql://root:[email protected]/coffeetest ';$map=Array();$DBI->fetchmap ("SHOW TABLES",$map);$tables=Array_keys($map); for($i= 0;$iCount($tables);$i++){ Echo($tables[$i]." \ n "); $sql= "SHOW INDEX from".$tables[$i]; $list=$DBI->fetchall ($sql); $indexs=Array(); foreach($list as $item){ $indexs[$item[' Key_name '] [] =$item[' column_name ']; } $j= 0; $list=Ar

196. Delete Duplicate EmailsQuestion Editorial Solution submissions total accepted:15426 total submissions:81201 difficulty:easy Write a SQL query to delete all duplicate emails entries in a table named who, keeping only unique emails based on its s Mallest Id. +----+------

In order to experiment with duplicate data, a design is not very good (no primary key) table and insert some duplicate data:Create Database testdbuse testdb; gocreate table DUPSNOPK (Col1 int null, Col2 char (5) null); Goinsert DUPSNOPK (col1,col2) Va Lues (1, ' abc '), (2, ' abc '), (2, ' abc '), (2, ' abc '), (7, ' XYZ '), ( 7, ' XYZ ');To verify that the table does have

-->--> (Roy) generation if not object_id (' tempdb ... #t ') is null drop table #t Go CREATE TABLE #t ([num] int,[name] nvarchar (1)) Insert #t Select 1,n ' A ' union ALL Select 1,n ' A ' union ALL Select 1,n ' A ' union ALL Select 2,n ' B ' UNION ALL Select 2,n ' B ' Go Method 1: If object_id (' tempdb.. # ') is not nullDROP TABLE #SELECT DISTINCT * into # from #t--Exclude duplicate record result set generate temp

With SQL statements, delete duplicates only keep oneIn thousands of records, there are some same records, how can you use SQL statements, delete duplicates1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determineSelect

Oracle SQL code www.2cto.com create table test (col VARCHAR2 (20) insert into test VALUES ('A'); insert into test VALUES ('B '); insert into test VALUES ('C'); insert into test VALUES ('A'); insert into test VALUES ('C'); COMMIT; -- DELETE duplicate data DELETE test t where rowid

Delete duplicate faces In ArcMap (09:47:26) Reprinted Tags:Miscellaneous Classification: ArcGIS There are many specific methods. Here are some solutions for you to learn. First: 1. Use polygon to line to convert the surface into line new_line2. Use feature to polygon to convert the line into a new_polygonNote: To maintain the attributes of the original surface, use featur

This article explains how PHP queries and removes multiple columns of data from a database. Share to everyone for your reference, as follows: $result =mysql_query ($sql _del, $con);} Some code mysql_close ($con);? > More readers interested in PHP related content can view the topic: "PHP Primer for Object-oriented programming", "PHP String Usage Summary", "Php+mysql Database Operations Primer" and "PHP common database Operation Skills Summar

Query and delete duplicate records SQL statement 1, find redundant records in the table, duplicate records are based on a single field (ID) to determine select * from table where Id in (select Id from table group Byid having count (ID) > 1) 2, delete redundant records in the

Example of deleting duplicate records in a data table in SQL Server, SQL Server [Project] The users table in the database contains the u_name and u_pwd fields. The u_name contains duplicate items. Now we need to delete duplicate i

Label:ID Name Course Name score1 Zhang Three Mathematics 692 John Doe Mathematics 893 Zhang Three Mathematics 69Delete the same student redundancy information except for the automatic numberingThe complete SQL statement is as follows:DELETE from TableName where-id not-in (select-Bid from (select min (id) as-bid from TableName GROUP by Name,kecheng,fenshu) as b);Explain:Select Bid from (select min (id) as bid from TableName Group by Name,kecheng,fenshu

Title: MySQL Database delete duplicate dataBecause it is MySQL, other data crying commands are not available in MySQL. Don't assume that SQL scripts are useddelete from Table1where field1 in ( select field1 from table1 group by field1 having count (field1) > 1 ) and rowid not in (select min (ROWID) from table1 group by field1 having count (fi

Just at the beginning, according to my idea, this is very simple, on the SQL statement Delete from ZQZRDP where is tel in (select min (dpxx_id) from ZQZRDP GROUP BY Tel has count (tel) >1); Execute, Error!! ~! ~ The exception means: You cannot specify the update of the target table in the FROM clause. Silly, MySQL write like this, no, let a person depressed. Can only be divided into steps,

SQL statements remove duplicate records, get duplicate records --Query a table to effectively remove duplicate records, UserID as a self-growing primary key, Roleid as a repeating field The code is as follows Copy Code SELECT MIN (UserID) as UserID, Roleid from Tmptable GROUP by RoleidSELE