FOR UPDATE cursor的基本语法 [英] Basic syntax on FOR UPDATE cursor
问题描述
好吧,我当然很熟悉使用只读游标浏览表格,但我似乎找不到实际更新当前行的正确语法(< a href =http://msdn.microsoft.com/en-us/library/ms180169%28v=SQL.90%29.aspx =nofollow>光标页和 UPDATE page 在线书籍似乎显示这个简单的操作):
Ok, I'm certainly familiar with walking through a table using a read-only cursor, but I can't seem to find the right syntax for actually updating the current row (Neither the cursor page nor the UPDATE page in books online seems to show this simple operation):
DECLARE @counter int;
SET @counter = 1;
DECLARE myCursor CURSOR FOR
SELECT RowID, Value FROM myTable
FOR UPDATE OF Value;
OPEN myCursor;
WHILE @counter < 100
FETCH NEXT FROM myCursor
UPDATE myCursor SET Value = @Counter << DOESN'T WORK
SET @counter = @counter + 1
END
CLOSE myCursor
DEALLOCATE myCursor
我也尝试过 SET Value = @Counter
并使用 INTO @Value
在FETCH上,但似乎不能得到这样工作。
I also tried just SET Value = @Counter
and using an INTO @Value
on the FETCH, but couldn't seem to get that to work either.
这显然过于简化,有更有效的方法只是计数列。
This is obviously over-simplified, there are much more efficient ways to just "count" down a column. I won't bore you with the actual calculation.
是的,我需要一个游标,而不是整个表上的UPDATE(每个连续行的值将是基于取决于先前行已经被写入的计算)。
Yes, I do need a cursor and not an UPDATE on the entire table (the value for each successive row will be based on a calculation that depends on the prior row already being written).
最初在SQL 2005上测试,但是我需要将代码移植到SQL 2000和2008以及。谢谢!
Testing this initially on SQL 2005, but I will need to port the code to SQL 2000 and 2008 as well. Thanks!
推荐答案
您要使用 WHERE CURRENT OF
-
You want to use WHERE CURRENT OF
-
DECLARE complex_cursor CURSOR FOR
SELECT a.BusinessEntityID
FROM HumanResources.EmployeePayHistory AS a
WHERE RateChangeDate <>
(SELECT MAX(RateChangeDate)
FROM HumanResources.EmployeePayHistory AS b
WHERE a.BusinessEntityID = b.BusinessEntityID) ;
OPEN complex_cursor;
FETCH FROM complex_cursor;
UPDATE HumanResources.EmployeePayHistory
SET PayFrequency = 2
WHERE CURRENT OF complex_cursor;
CLOSE complex_cursor;
DEALLOCATE complex_cursor;
GO
这来自 MSDN 。
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