的毗连特定字符串的每一个插入的行

Question

这是一个假设的例子..

我试图找到一个很好的办法，以确保每一个插在我的表mytable的特定列col1值都有一个特定的字符串http://开头的值。

例子：

我想插入myprofile到mytable左右（经过我的检查条件..）终值将http://myprofile

我想，一个很好的办法可以使用插入时的触发，但我没有找到具体的东西..

任何想法？

谢谢。

Answer 1

你可以尝试这样的事情作为一个起点 - 这是SQL Server（不知道MySQL的不够好，为您提供该触发代码）：

-- create the trigger, give it a meaningful name 
CREATE TRIGGER PrependHttpPrefix 
ON dbo.YourTableName   -- it's on a specific table 
AFTER INSERT, UPDATE   -- it's for a specific operation, or several 
AS 
BEGIN 
    -- the newly inserted rows are stored in the "Inserted" pseudo table. 
    -- It has the exact same structure as your table that this trigger is 
    -- attached to. 
    -- SQL Server works in such a way that if the INSERT affected multiple 
    -- rows, the trigger is called *once* and "Inserted" contains those 
    -- multiple rows - you need to work with "Inserted" as a multi-row data set 
    -- 
    -- You need to join the "Inserted" rows to your table (based on the 
    -- primary key for the table); for those rows newly inserted that 
    -- **do not** start with "http://" in "YourColumn", you need to set 
    -- that column value to the fixed text "http:/" plus whatever has been inserted 
    UPDATE tbl 
    SET YourColumn = 'http://' + i.YourColumn 
    FROM dbo.YourTableName tbl 
    INNER JOIN Inserted i ON tbl.PKColumn = i.PKColumn 
    WHERE LEFT(i.YourColumn, 7) <> 'http://' 
END