【優化SQL Server迴圈更新、插入耗時長的問題】
一： 工作當中遇到更新較多資料時，使用迴圈(while,或遊標)進行增刪改時，特別費時
WHILE @i <= @rows
BEGIN
SELECT @appNo = AppNumber, @roleid = RoleId, @statusi= Status, @empId = EmployeeId FROM #Atable WHERE ID = @i
IF EXISTS(SELECT 1 FROM Btable WHERE AppNumber = @appNo AND RoleID = @roleid AND EmployeeId = @empId)
BEGIN
UPDATE Btable
SET Status = @statusi, CreatedBy = NULL, ModifiedOn = GETDATE()
WHERE AppNumber = @appNoi AND RoleId = @roleidi AND EmployeeId = @empId
END
ELSE
BEGIN
INSERT INTO Btable(EmployeeId, AppNumber, RoleId, Status, CreatedOn, CreatedBy, ModifiedOn, ModifiedBy)
SELECT EmployeeId, AppNumber, RoleId, Status, GETDATE(), CreatedBy, GETDATE(), ModifiedBy FROM #Atable WHERE ID = @i
END
SELECT @i= @i + 1
END
二：利用表左、右連線進行批量刪除解決迴圈增刪改耗時長的問題
update aru set aru.Status = arul.Status, aru.ModifiedOn = GETDATE()
from Btable as aru
inner join Atable as arul
on aru.AppNumber = arul.AppNumber and aru.RoleId = arul.RoleId and aru.EmployeeID = arul.EmployeeID
三：A,B兩張表中有可能資料不相等，可以宣告兩個變數@count1,@count2
DECLARE @Count1 int,@Count2 int
select @Count1 = COUNT(1) from Atable
select @Count2 = COUNT(1) from Btable
四： 根據@count1和@count2的大小判斷是否新增還是刪除
IF(@Count1 > @Count2)
BEGIN
SELECT * INTO Btable
from Atable as arul
left join Btable as aru
on aru.AppNumber = arul.AppNumber and aru.RoleId = arul.RoleId and aru.EmployeeID = arul.EmployeeID
where aru.AppNumber is null and aru.RoleId is null and aru.EmployeeID is null
END
ELSE
BEGIN
update aru set aru.Status = 0
from Btable as aru
left join Atable as arul
on aru.AppNumber = arul.AppNumber and aru.RoleId = arul.RoleId and aru.EmployeeID = arul.EmployeeID
where arul.AppNumber is null and arul.RoleId is null and arul.EmployeeID is null
END
個人工作中總結出來，如有轉載請註明出處！