游标有什么用? [英] What is the useful of cursor?

问题描述

DECLARE @name VARCHAR(50) -- database name
DECLARE @path VARCHAR(256) -- path for backup files
DECLARE @fileName VARCHAR(256) -- filename for backup
DECLARE @fileDate VARCHAR(20) -- used for file name

SET @path = 'C:\Backup\'

SELECT @fileDate = CONVERT(VARCHAR(20),GETDATE(),112)

DECLARE db_cursor CURSOR FOR
SELECT name
FROM MASTER.dbo.sysdatabases
WHERE name NOT IN ('master','model','msdb','tempdb')

OPEN db_cursor
FETCH NEXT FROM db_cursor INTO @name

WHILE @@FETCH_STATUS = 0
BEGIN
       SET @fileName = @path + @name + '_' + @fileDate + '.BAK'
       BACKUP DATABASE @name TO DISK = @fileName

       FETCH NEXT FROM db_cursor INTO @name
END

CLOSE db_cursor
DEALLOCATE db_cursor

http://www.mssqltips.com/sqlservertip/1599/sql-server-cursor-example / [ ^ ]

http://www.mssqltips.com/sqlservertip/1599/sql-server-cursor-example/[^]

推荐答案

在许多情况下，您需要遍历Sql-Server中的对象，因此需要使用Cursors.在您的示例中，查询了一些数据库，然后在生成的路径中一个接一个地创建了它们的备份文件.
为了找到游标的优点/缺点，请看一下这篇文章:

http://www.allinterview.com/showanswers/61552.html [

In many situations you need to iterate through objects in Sql-Server so you need to use Cursors. In your example, a few databases are queried and then their backup files is created in a generated path one by one.
In order to find advantages/disadvantages of Cursors, take a look at this post:

http://www.allinterview.com/showanswers/61552.html[^]

Cheers.

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