將mySQL觸發器轉換爲TSQL

Question

尋找將此mySQL觸發器轉換爲TSQL的幫助。

CREATE TRIGGER IF not exists TF_WATCHLIST_PERSISTENCE_ADD_POSITION 
AFTER INSERT ON TF_WATCHLIST_PERSISTENCE 
FOR EACH ROW 
WHEN NEW.WATCHLIST_POSITION IS NULL 
BEGIN 
    UPDATE TF_WATCHLIST_PERSISTENCE SET 
    WATCHLIST_POSITION = (SELECT COUNT(*) - 1 FROM TF_WATCHLIST_PERSISTENCE WHERE WATCHLIST_USER = NEW.WATCHLIST_USER) 
    WHERE rowid = NEW.rowid; 
END; 

Answer 1

試試這個：

CREATE TRIGGER TF_WATCHLIST_PERSISTENCE_ADD_POSITION ON TF_WATCHLIST_PERSISTENCE AFTER INSERT 
AS 
BEGIN 
    WITH DataSource AS 
    (
     SELECT DS.WATCHLIST_USER 
       ,COUNT(*) - 1 AS WATCHLIST_POSITION 
     FROM TF_WATCHLIST_PERSISTENCE DS 
     INNER JOIN inserted I 
      ON DS.WATCHLIST_USER = I.WATCHLIST_USER 
     WHERE inserted.WATCHLIST_POSITION is null 
     GROUP BY DS.WATCHLIST_USER 
    ) 
    UPDATE TF_WATCHLIST_PERSISTENCE 
    SET WATCHLIST_POSITION = DS.[WATCHLIST_POSITION] 
    FROM TF_WATCHLIST_PERSISTENCE DS 
    INNER JOIN DataSource I 
     ON DS.WATCHLIST_USER = I.WATCHLIST_USER; 
END 

Answer 2

我懷疑你正在尋找一個排名功能，或每用戶甚至一個簡單的COUNT(*)？ MySQL在analytic，ranking或窗口函數中相當差，所以使用諸如奇怪更新或觸發器等技巧來模擬它們。

在SQL Server中，你可以返回的單個用戶與COUNT()每一行應用在單個用戶相匹配的記錄相匹配的記錄數：

SELECT *, COUNT(*) OVER (PARTITION BY WATCHLIST_USER) 
FROM TF_WATCHLIST_PERSISTENCE 

無需觸發。您可以使用任何具有OVER（）子句的聚合。

如果您想按照某種順序排列排名，您可以使用ROW_NUMBER()或RANK（）等排名函數之一。如果要計算基於每個用戶的一排位置，例如在創建日期，你可以寫：

SELECT *, ROW_NUMBER(*) OVER (PARTITION BY WATCHLIST_USER ORDER BY CreationDate) 
FROM TF_WATCHLIST_PERSISTENCE 

如果你有，你可以用它來生成一個row position每用戶

SELECT *, ROW_NUMBER(*) OVER (PARTITION BY WATCHLIST_USER ORDER BY ID) 
FROM TF_WATCHLIST_PERSISTENCE 

一個遞增的ID大多數時候，你不需要需要存儲的行位置。向查詢添加排名功能很簡單。

如果你需要存儲在表中這樣的行位置，你可以使用一個簡單的多行觸發器

CREATE TRIGGER TF_WATCHLIST_PERSISTENCE_ADD_POSITION 
ON TF_WATCHLIST_PERSISTENCE 
AFTER INSERT, UPDATE 
AS 
    update TF_WATCHLIST_PERSISTENCE 
    set WATCHLIST_POSITION =ROW_NUMBER() OVER (PARTITION BY WATCHLIST_USER ORDER BY ID) 
    FROM inserted 
    INNER JOIN TF_WATCHLIST_PERSISTENCE on inserted.ID=TF_WATCHLIST_PERSISTENCE.ID 

或者

update TF_WATCHLIST_PERSISTENCE 
set WATCHLIST_POSITION =ROW_NUMBER() OVER (PARTITION BY WATCHLIST_USER ORDER BY ID) 
FROM inserted 
INNER JOIN TF_WATCHLIST_PERSISTENCE 
    ON inserted.WATCHLIST_USER =TF_WATCHLIST_PERSISTENCE.WATCHLIST_USER 

如果要插入新的條目現有用戶並重新計算所有職位

Answer 3

感謝您的全力幫助

我結束了這一點。

CREATE TRIGGER TF_WATCHLIST_PERSISTENCE_ADD_POSITION 
ON TF_WATCHLIST_PERSISTENCE 
AFTER INSERT, UPDATE 
AS 
DECLARE @MyCursor CURSOR; 
DECLARE @MyField_USER varchar(250); 
DECLARE @MyField_ID varchar(250); 
DECLARE @MyField_NewPos int 

BEGIN 
SET @MyCursor = CURSOR FOR 
SELECT  WATCHLIST_USER 
     , WATCHLIST_ID 
FROM inserted 
WHERE inserted.WATCHLIST_POSITION is null 

OPEN @MyCursor 
FETCH NEXT FROM @MyCursor 
INTO @MyField_USER, @MyField_ID 

WHILE @@FETCH_STATUS = 0 

BEGIN 
    set @MyField_NewPos = (SELECT MAX(WATCHLIST_POSITION) + 1 FROM TF_WATCHLIST_PERSISTENCE WHERE WATCHLIST_USER = @MyField_USER) 
    print @MyField_NewPos 

    update TF_WATCHLIST_PERSISTENCE 
     SET WATCHLIST_POSITION = ISNULL(@MyField_NewPos,0) 
     WHERE  WATCHLIST_USER = @MyField_USER 
      AND  WATCHLIST_ID = @MyField_ID 
      AND  WATCHLIST_POSITION IS NULL 

     Print @MyField_USER 
     Print @MyField_ID 
     FETCH NEXT FROM @MyCursor 
     INTO @MyField_USER, @MyField_ID 
END; 


END; 
CLOSE @MyCursor