sql server 游标的使用

A. 在简单的游标中使用 FETCH

下例为 authors 表中姓以字母 B 开头的行声明了一个简单的游标，并使用 FETCH NEXT 逐个提取这些行。FETCH语句以单行结果集形式返回由 DECLARE CURSOR 指定的列的值。

USE pubs
GO
DECLARE authors_cursor CURSOR FOR
SELECT au_lname FROM authors
WHERE au_lname LIKE "B%"
ORDER BY au_lname

OPEN authors_cursor

-- Perform the first fetch.
FETCH NEXT FROM authors_cursor

-- Check @@FETCH_STATUS to see if there are any more rows to fetch.
WHILE @@FETCH_STATUS = 0
BEGIN
   -- This is executed as long as the previous fetch succeeds.
   FETCH NEXT FROM authors_cursor
END

CLOSE authors_cursor
DEALLOCATE authors_cursor
GO

au_lname                                 
---------------------------------------- 
Bennet                                   
au_lname                                 
---------------------------------------- 
Blotchet-Halls                           
au_lname                                 
----------------------------------------

B. 使用 FETCH 将值存入变量

下例与上例相似，但 FETCH 语句的输出存储于局部变量而不是直接返回给客户端。PRINT 语句将变量组合成单一字符串并将其返回到客户端。

USE pubs
GO

-- Declare the variables to store the values returned by FETCH.
DECLARE @au_lname varchar(40), @au_fname varchar(20)


DECLARE authors_cursor CURSOR FOR
SELECT au_lname, au_fname FROM authors
WHERE au_lname LIKE "B%"
ORDER BY au_lname, au_fname

OPEN authors_cursor

-- Perform the first fetch and store the values in variables.
-- Note: The variables are in the same order as the columns
-- in the SELECT statement. 

FETCH NEXT FROM authors_cursor
INTO @au_lname, @au_fname

-- Check @@FETCH_STATUS to see if there are any more rows to fetch.
WHILE @@FETCH_STATUS = 0
BEGIN

   -- Concatenate and display the current values in the variables.
   PRINT "Author: " + @au_fname + " " +  @au_lname

   -- This is executed as long as the previous fetch succeeds.
   FETCH NEXT FROM authors_cursor
   INTO @au_lname, @au_fname
END

CLOSE authors_cursor
DEALLOCATE authors_cursor
GO

Author: Abraham Bennet
Author: Reginald Blotchet-Halls