尝试更改一些存储过程和查询以获得更好的性能。对于某些部分,它正在重写游标语法。为此,我必须充分了解它们的工作原理。我尝试了这个简单的 ETL 示例,但它没有给我预期的结果。基本上,在此处使用光标执行 UPSERT。
示例代码:
CREATE TABLE #Destination
(PersonID INT, FirstName VARCHAR(10), LastName VARCHAR (10))
INSERT INTO #Destination VALUES (101, 'M', 'Donalds')
INSERT INTO #Destination VALUES (102, NULL, 'Richards')
INSERT INTO #Destination VALUES (103, 'Rianna', 'Lock')
INSERT INTO #Destination VALUES (104, 'Leo', 'Svensson')
CREATE TABLE #SourceTable
(PersonID INT, FirstName VARCHAR(10), LastName VARCHAR (10))
INSERT INTO #Destination VALUES (102, 'Diana', 'Richards')
INSERT INTO #SourceTable VALUES (103, 'Rianna', 'Locks')
INSERT INTO #SourceTable VALUES (106, 'Cleo', 'Davung')
DECLARE @PersonID INT
DECLARE @Firstname VARCHAR (10)
DECLARE @Lastname VARCHAR (10)
DECLARE SimpleCursor CURSOR FOR
SELECT PersonID, FirstName, LastName
FROM #SourceTable
Open SimpleCursor
FETCH NEXT FROM SimpleCursor INTO @PersonID, @Firstname, @Lastname
WHILE @@FETCH_STATUS = 0
BEGIN
IF EXISTS ( SELECT PersonID FROM #Destination
WHERE PersonID = @PersonID )
UPDATE #Destination
SET #Destination.FirstName = #SourceTable.FirstName,
#Destination.LastName = #SourceTable.LastName
FROM #SourceTable
WHERE #Destination.PersonID = #SourceTable.PersonID
ELSE
INSERT INTO #Destination
SELECT PersonID, Firstname, Lastname FROM #SourceTable
FETCH NEXT FROM SimpleCursor INTO @PersonID, @Firstname, @Lastname
END
CLOSE SimpleCursor
DEALLOCATE SimpleCursor
SELECT * FROM #Destination
我在这里错过了什么?我没有更新任何东西,而 PersonID 102 和 103 确实存在。
非常感谢。
最佳答案
您没有在 UPDATE
或 INSERT
语句中使用将值提取到其中的变量。尝试:
...
IF EXISTS (SELECT *
FROM #Destination
WHERE PersonID = @PersonID)
BEGIN
UPDATE #Destination
SET FirstName = @FirstName,
LastName = @LastName
WHERE PersonID = @PersonID;
END
ELSE
BEGIN
INSERT INTO #Destination
(PersonID,
FirstName,
LastName)
VALUES (@PersonID,
@FirstName,
@LastName);
END;
...
关于sql-server - 了解游标的工作原理,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51485438/