使用concat列联接表

Question

So I have two tables I want to join using SQL.

Since they did not have a common column I used

SELECT NEW_ID = CONCAT ('0',table1.ID)

Now that I have the new column with matching data in both tables, how do I join both tables? Is there any way to use the NEW_ID column as a temporary column so that I do not have to alter table 1?

Answer 1

In your case, suitable. of course in terms of performance it is not the best solution ( compare fields with diffrent types)

Select * 
From Table1 As t1 inner join Table2 as t2
     ON t1.ID = CAST(t2.ID AS INT)

Answer 2

You Can Just give the Concrete Expression in the Join.You Don't have to add a new Column For that. Like this

SELECT
  *
   FROM Table1 A
       INNER JOIN Table2 B
          ON RIGHT('00'+A.Id,2) = RIGHT('00'+B.Id,2)

Answer 3

Different ways, here's one:

 ;WITH CTE AS 
 (
 SELECT NEW_ID = CONCAT ('0',table1.ID) FROM TableA
 )

 SELECT * FROM CTE AS C INNER JOIN TableB AS B ON C.New_ID = B.ID