为什么运行程序时会一次向数据库插入两条相同记录？

这两句分别插入了一条记录，因此得到两条：

// getDataSet的参数是一条插入语句，因此很可能内部做了插入数据的动作；

DataSet ds = d.getDataSet(sql, "R_HiddenDangerInstruct_Order")

// 再次插入一条

return d.exec(sql)

在使用SQL数据库的时候，我们也许会需要一次像数据库中添加多条记录，那么我们可以使用SQL语句来实现，该语句具体如下：

--添加一条记录

INSERT INTO tableName(col1,col2,col3) VALUES (1,2,3)

--添加多条记录

INSERT INTO tableName(col1,col2,col3)

SELECT 3,4,5

UNION ALL

SELECT 6,7,8

--从另外的一张表中读取多条数据添加到新表中

INSERT INTO tableName(col1,col2,col3)

SELECT a,b,c FROM tableA

--从其他的多张表中读取数据添加到新表中

INSERT INTO tableName(col1,col2,col3)

SELECT a,b,c FROM tableA WHERE a=1

UNION ALL

SELECT a,b,c FROM tableB WHERE a=2

上边代码中的into都可以省略！

上边代码中的union all如果换成union，则相同记录只插入一次，不会重复插入。

另外一种方法是SQL Server2008特有的，所以，如果你不是SQL Server2008，就不能使用这种方法了。

INSERT INTO MyTable(ID,NAME)VALUES(7,'003'),(8,'004'),(9,'005')

create table [TEST]

(

[NUM_ID] int primary key

)

go

declare @temp int

set @temp=1

while @temp<=1000000

begin

insert into [TEST]([NUM_ID]) values(@temp)

set @temp=@temp+1

end

go

----------------------------------------------------------

--试试下面的方法

--2005

DECLARE @n AS BIGINT

SET @n = 1000000

WITH Base AS

(

SELECT 1 AS n

UNION ALL

SELECT n + 1 FROM Base WHERE n <CEILING(SQRT(@n))

),

Expand AS

(

SELECT 1 AS c

FROM Base AS B1, Base AS B2

),

Nums AS

(

SELECT ROW_NUMBER() OVER(ORDER BY c) AS n

FROM Expand

)

SELECT n FROM Nums WHERE n <= @n

OPTION(MAXRECURSION 0)

--2

CREATE FUNCTION dbo.fn_nums(@n AS BIGINT) RETURNS TABLE

AS

RETURN

WITH

L0 AS(SELECT 1 AS c UNION ALL SELECT 1),

L1 AS(SELECT 1 AS c FROM L0 AS A, L0 AS B),

L2 AS(SELECT 1 AS c FROM L1 AS A, L1 AS B),

L3 AS(SELECT 1 AS c FROM L2 AS A, L2 AS B),

L4 AS(SELECT 1 AS c FROM L3 AS A, L3 AS B),

L5 AS(SELECT 1 AS c FROM L4 AS A, L4 AS B),

Nums AS(SELECT ROW_NUMBER() OVER(ORDER BY c) AS n FROM L5)

SELECT n FROM Nums WHERE n <= @n

GO

--2000 这个会比前两个慢，但是前两个2000不能用

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 Nums VALUES(1)

WHILE @rc * 2 <= @max

BEGIN

INSERT INTO dbo.Nums SELECT n + @rc FROM dbo.Nums

SET @rc = @rc * 2

END

INSERT INTO dbo.Nums

SELECT n + @rc FROM dbo.Nums WHERE n + @rc <= @max

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