Detailed introduction to eliminating duplicate rows

This article mainly introduces some methods of eliminating duplicate rows in MySQL. Friends in need can refer to the sql statement/* MySQL some methods to eliminate duplicate rows ---Chu Minfei ---2010-08-12 22:49:44.660 --Please indicate the source for quotations and reprints: http://blog.csdn.NET/feixianxxx */ ----------------All fields are repeated----------------------------- --1 Use table replacement to remove duplicates create table test_1(id int,value int); insert test_1 select 1,2 union all select 1,2 un

1. Analysis of how MySQL eliminates duplicate rows

Introduction: This article mainly introduces some methods of eliminating duplicate rows in MySQL. Friends in need can refer to

2 . sql Advanced query operator UNION EXCEPT right and external connection

Introduction: sql Advanced query operator union except right and external connection a: union operator The union operator derives a result table by combining two other result tables (such as table1 and table2) and eliminating any duplicate rows in the tables. When all is used with union (that is, union all), duplicate rows are not eliminated. In both cases, every row in the derived table comes from either table1 or table2. sq

3. sql Common Operation Operators (UNION EXCEPT INTERSECT sp_renamedb)

Introduction: SQL Common Operation Operators symbol (union except intersect left sp_renamedb) Several advanced query operators a: union operator The union operator derives a result table by combining two other result tables (such as table1 and table2) and eliminating any duplicate rows in the tables. When all is used with union (that is, union all), duplicate rows are not eliminated. In both cases, each row of the derived table

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