Question

在此case

的答案中

由于性能原因，建议不要使用游标。在更新触发器中循环更新数据的最佳实践是什么？

更新：

以下是用于创建该更新触发器的TSQL。

CREATE TRIGGER [dbo].[trAfterUpdateInfoDoc]
ON [dbo].[InfoDocs]
AFTER UPDATE
AS
BEGIN
    DECLARE @infodoctemplateid INT;
    DECLARE @infodocid INT;
    DECLARE @requireccount FLOAT(2);
    DECLARE @filledcount FLOAT(2);
    DECLARE @pcnt FLOAT(2);

    DECLARE c CURSOR FOR
         SELECT id 
         FROM InfoDocs ifd 
         WHERE exists (SELECT 1 FROM Inserted AS i WHERE i.id = ifd.id)

    OPEN c

    FETCH NEXT FROM c INTO @infodocid

    WHILE @@Fetch_Status = 0 
    BEGIN
        SELECT @infodoctemplateid = InfoDocTemplateId 
        FROM InfoDocs 
        WHERE id = @infodocid;

        SELECT @requireccount = COUNT(*) 
        FROM InfoDocTemplateFields 
        WHERE InfoDocTemplateId = @infodoctemplateid 
          AND IsRequired = 1;

        IF (@requireccount = 0)
        BEGIN
            set @pcnt = 100;
        END
        ELSE
        BEGIN
            select @filledcount = count(*) from InfoDocFields 
            where InfoDocId = @infodocid 
            and InfoDocTemplateFieldId in (select id from InfoDocTemplateFields where InfoDocTemplateId = @infodoctemplateid and IsRequired = 1)
            and (BooleanValue is not null or (StringValue is not null and StringValue <> '') or IntValue is not null or DateValue is not null)

            set @pcnt = @filledcount / @requireccount * 100.0;
        END
        update InfoDocs set PercentageCompleted = @pcnt Where id = @infodocid;

        Fetch next From c into @infodocid
    End
Close c
Deallocate c
END

Answer 1

我已经尝试将您的光标转换为基于集合的代码，但是我没有办法测试我的解决方案是否正确，而且昨晚我睡不着，所以我可能在这里错过了一些东西，在那里-它可能是比我编写的代码更短，更有效的代码，但它应该为您提供一个良好的起点：

CREATE TRIGGER [dbo].[trAfterUpdateInfoDoc]
ON [dbo].[InfoDocs]
AFTER UPDATE
AS
BEGIN
    WITH CTE1 AS
    (
        SELECT  ifd.Id, 
                SUM(CASE WHEN IsRequired = 1 THEN 1 ELSE 0 END) As RequiredCount,
                (
                    select count(*) 
                    from InfoDocFields 
                    where InfoDocFields.InfoDocId = ifd.Id,
                    and InfoDocTemplateFieldId in (
                        select id 
                        from InfoDocTemplateFields 
                        where InfoDocTemplateId = idtf.InfoDocTemplateId 
                        and IsRequired = 1
                    )
                    and 
                        InfoDocFields.BooleanValue is not null 
                        or (InfoDocFields.StringValue is not null and InfoDocFields.StringValue <> '') 
                        or InfoDocFields.IntValue is not null 
                        or InfoDocFields.DateValue is not null

                ) As Filledcount
        FROM InfoDocs ifd 
        JOIN InfoDocTemplateFields idtf
            ON ifd.InfoDocTemplateId = idtf.InfoDocTemplateId
        WHERE exists (SELECT 1 FROM Inserted AS i WHERE i.id = ifd.id)
        GROUP BY ifd.Id, idtf.InfoDocTemplateId
    ), CTE2 AS
    (
        SELECT  ifd.Id, 
                CASE WHEN RequiredCount = 0 THEN 
                    100
                ELSE
                    Filledcount / RequiredCount * 100.0
                END As Completed
        FROM CTE1
    )

    UPDATE docs 
    SET PercentageCompleted = Completed 
    FROM InfoDocs docs
    JOIN cte2 
        ON docs.id = cte2.Id

END

Answer 2

您可以通过对联接进行更新来摆脱光标。

例如

UPDATE t1
SET Col2 = t2.Col2,
Col3 = t2.Col3
FROM Table1 t1
INNER JOIN Table2 t2 ON t1.Col1 = t2.Col1
WHERE t1.Col1 IN (21, 31)

这将为您提供最佳性能。并且代码将更加紧凑和易于理解。

TSQL替代方法，用于游标循环遍历更新触发数据

2 个答案: