Home/ Questions/Q 3611636
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-18T21:54:00+00:00

I have two tables: T1: | M_ID | P_ID1 | P_ID2 | rest of

  • 0

I have two tables:
T1:

| M_ID | P_ID1 | P_ID2 | rest of T1 columns |
|  0   |   0   |   1   |         ...        |
|  1   |   2   |   3   |         ...        |

T2:

| P_ID | Type | A | B |
|  0   |   1  | a | e |
|  1   |   2  | b | f |
|  2   |   1  | c | g |
|  3   |   2  | d | h |

Now, I want to have a query that selects this:

| M_ID | P_1a | P_1b | P_2a | P_2b | rest of T1 columns |
|  0   |  a   |  e   |  b   |  f   |         ...        |
|  1   |  c   |  g   |  c   |  h   |         ...        |

So, in words: I want to select all columns from T1, but I want to replace P_ID1 with the columns from T2, where the P_ID is equal to P_ID1, and the type is 1, and basically the same for P_ID2.

I can obviously get the information I need with multiple queries, but I was wondering if there is a way that I can do this with one query. Any ideas?

I’m currently using SQL Server 2008r2, but I’d also be interested in solutions for other database software.

Thanks for the help!

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Sure, you just need to use a join:

    select T1.M_ID, t2_1.A as P_1a, t2_1.B as P_1b, t2_2.A as P_2a, t2_2.B as P_2b, ...
from T1, T2 t2_1, T2 t2_2
where T1.P_ID1 = t2_1.P_ID and T1.P_ID2 = t2_2.P_ID

    basically we are joining T1 onto T2 twice, once for the P_1 values and a second time for the P_2 values. You need to alias T2 when you join it twice to distinguish between the two (that’s what the t2_1 and t2_2 are – a means of distinguishing between the two instances of the joined T2).

    • 0