将mySQL触发器转换为TSQL

Question

寻找将此mySQL触发器转换为TSQL的帮助。

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

试试这个：

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

我怀疑你正在寻找一个排名功能，或每用户甚至一个简单的COUNT(*)？ MySQL在analytic，ranking或窗口函数中相当差，所以使用诸如奇怪更新或触发器等技巧来模拟它们。

在SQL Server中，你可以返回的单个用户与COUNT()每一行应用在单个用户相匹配的记录相匹配的记录数：

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

无需触发。您可以使用任何具有OVER（）子句的聚合。

如果您想按照某种顺序排列排名，您可以使用ROW_NUMBER()或RANK（）等排名函数之一。如果要计算基于每个用户的一排位置，例如在创建日期，你可以写：

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

如果你有，你可以用它来生成一个row position每用户

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

一个递增的ID大多数时候，你不需要需要存储的行位置。向查询添加排名功能很简单。

如果你需要存储在表中这样的行位置，你可以使用一个简单的多行触发器

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 

如果要插入新的条目现有用户并重新计算所有职位

Answer 3

感谢您的全力帮助

我结束了这一点。

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