Microsoft SQL Server 基本仅前进光标
示例
通常，您会希望避免使用游标，因为它们会对性能产生负面影响。但是，在某些特殊情况下，您可能需要逐条记录遍历数据记录并执行一些操作。
DECLARE @orderId AS INT
-- here we are creating our cursor, as a local cursor and only allowing
-- forward operations
DECLARE rowCursor CURSOR LOCAL FAST_FORWARD FOR
-- this is the query that we want to loop through record by record
SELECT [OrderId]
FROM [dbo].[Orders]
-- first we need to open the cursor
OPEN rowCursor
-- now we will initialize the cursor by pulling the first row of data, in this example the [OrderId] column,
-- and storing the value into a variable called @orderId
FETCH NEXT FROM rowCursor INTO @orderId
-- start our loop and keep going until we have no more records to loop through
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT @orderId
-- this is important, as it tells SQL Server to get the next record and store the [OrderId] column value into the @orderId variable
FETCH NEXT FROM rowCursor INTO @orderId
END
-- this will release any memory used by the cursor
CLOSE rowCursor
DEALLOCATE rowCursor
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