T-SQL Recipes之删除重复行

Posted 2020-07-07

一、准备基础数据

（1）创建辅助表，方便以后倾向于Set-base方式解决问题

-- Creating and Populating the Nums Auxiliary Table
SET NOCOUNT ON;
IF OBJECT_ID(‘dbo.Nums‘, ‘U‘) IS NOT NULL
    DROP TABLE dbo.Nums;

CREATE TABLE dbo.Nums(n INT NOT NULL PRIMARY KEY);

DECLARE @max AS INT ,
    @rc AS INT;

SET @max = 1000000;
SET @rc = 1;

INSERT  INTO dbo.Nums
        ( n )
VALUES  ( 1 );
WHILE @rc * 2 <= @max 
    BEGIN
        INSERT  INTO dbo.Nums
                ( n )
                SELECT  n + @rc
                FROM    dbo.Nums;
        SET @rc = @rc * 2;
    END
INSERT  INTO dbo.Nums
        ( n
        )
        SELECT  n + @rc
        FROM    dbo.Nums
        WHERE   n + @rc <= @max;
GO

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