Access SQL: Select from table if ID is in another - sql

Question

Say I have the table T1:
ID | PNo | MM | CP | Flag | Name |
---|-----|------|----|------|------|
1 | 13 | True | 4 | A | X |
1 | 92 | True | 3 | A | X |
2 | 1 | True | 3 | B | Y |
2 | 13 | False| 2 | A | Y |
3 | 13 | True | 3 | B | W |
4 | 1 | True | 3 | B | Z |
And T2:
ID | PNo | MM | CP |
---|-----|------|----|
1 | 13 | True | 4 |
2 | 92 | True | 3 |
3 | 1 | True | 3 |
4 | 13 | False| 2 |
5 | 13 | True | 3 |
1 | 1 | False| 3 |
What I want to do is to do a INSERT INTO where I take values of T1 and T2 but only if the ID of T2 is in T1 and if T1 has the flag with the value A.
I have tried two things:
1) INNER JOIN: Something like
INSERT INTO T3 (ID, PNo, MM, CP, Flag, Name)
SELECT T1.ID, T2.PNo, T2.MM, T2.CP, 'A', T1.Name
FROM T2 INNER JOIN T1 ON T1.ID = T2.ID
WHERE (T1.FLAG = 'A')
The problem here is that it literally takes every combination of all relevant rows from T1 and T2. What I want is, I only want to take those rows of T2 whose IDs are also in T1.
2) IN?
INSERT INTO T3 (ID, PNo, MM, CP, Flag, Name)
SELECT T1.ID, T2.PNo, T2.MM, T2.CP, 'A', T1.Name
FROM T2, T1
WHERE T2.ID IN
(SELECT ID FROM T1 WHERE Flag = 'X')
Problem here is, this takes foreeeeeeeeeeever!
Is there not a more sophisticated method for this?
edit:// Changed a value in T2 so that the example is more meaningful.
So what I want in the new table T3 is:
ID | PNo | MM | CP | Flag | Name |
---|-----|------|----|------|------|
1 | 13 | True | 4 | A | X |
1 | 1 | False| 3 | A | X |
2 | 1 | True | 3 | A | Y |
What I get instead is:
ID | PNo | MM | CP | Flag | Name |
---|-----|------|----|------|------|
1 | 13 | True | 4 | A | X |
1 | 1 | False| 3 | A | X |
1 | 13 | True | 4 | A | X |
1 | 1 | False| 3 | A | X |
2 | 1 | True | 3 | A | Y |
So basically for all T1 values that I select (ID, Name) and for all corresponding rows that I can match by ID in T2, I get every combination.

Answer 1

Your second solution is almost right, however, you perform cartesian product unnecessarily (I'm not surprised that it takes forever). Try this one and if it is slow then create an index on Flag.
INSERT INTO T3 (ID, PNo, MM, CP, Flag, Name)
SELECT *
FROM T2
WHERE T2.ID IN
(SELECT ID FROM T1 WHERE Flag = 'X')

Answer 2

This should do what you want:
INSERT INTO T3 (ID, PNo, MM, CP, Flag, Name)
SELECT T2.ID, T2.PNo, T2.MM, T2.CP, ?, "A"
FROM T2
WHERE T2.ID IN (SELECT ID FROM T1 WHERE Flag = "A");
You are selecting T1.ID in your first query. You can take either T1.ID or T2.ID, because you are requiring that they be equal.
You can do this with a JOIN:
INSERT INTO T3 (ID, PNo, MM, CP, Flag, Name)
SELECT T2.ID, T2.PNo, T2.MM, T2.CP, T1.Name, "A"
FROM T2 INNER JOIN
T1
ON T2.ID = T1.ID;
If this is generating duplicates, then you have multiple rows in T1 for a given name.