SQL Query - Ensure a row exists for each value in ()

Question

Currently struggling with finding a way to validate 2 tables (efficiently lots of rows for Table A)

I have two tables

Table A

 ID 
 A
 B 
 C

Table matched

ID Number
A   1
A   2
A   9
B   1
B   9
C   2

I am trying to write a SQL Server query that basically checks to make sure for every value in Table A there exists a row for a variable set of values ( 1, 2,9)

The example above is incorrect because t should have for every record in A a corresponding record in Table matched for each value (1,2,9). The end goal is:

Table matched

ID Number
A   1
A   2
A   9
B   1
B   2
B   9
C   1
C   2
C   9

I know its confusing, but in general for every X in ( some set ) there should be a corresponding record in Table matched. I have obviously simplified things.

Please let me know if you all need clarification.

Answer 1

Use:

  SELECT a.id
    FROM TABLE_A a
    JOIN TABLE_B b ON b.id = a.id
   WHERE b.number IN (1, 2, 9)
GROUP BY a.id
  HAVING COUNT(DISTINCT b.number) = 3

The DISTINCT in the COUNT ensures that duplicates (IE: A having two records in TABLE_B with the value "2") from being falsely considered a correct record. It can be omitted if the number column either has a unique or primary key constraint on it.

The HAVING COUNT(...) must equal the number of values provided in the IN clause.