SQL Server串联联接

Question

I want to create a left join between a concatenate result of two columns of the main table and another column of the second table. My question is, should this join affect the query performance? Is there any better way to do it?

Table A: Column1, Column2
Table B: Column3

---

Select *
from Table A left Outer Join
     Table B on Column1+Column2=Column3

I appreciate your help.

Thanks

Answer 1

This is fine,

For SQL Server

Select *
from `Table A` as a left Outer Join
     `Table B` as b on a.Column1 + a.Column2 = b.Column3

For MySQL use concat()

Select *
from `Table A` as a left Outer Join
     `Table B` as b on concat(a.Column1,a.Column2) = b.Column3