MySQL 3列查询返回重复项

Question

x_Id  | y_Id | z_Id
----- |----- |-----
1     | 1    | 1
2     | 1    | 1
3     | 1    | 1
4     | 1    | 1
5     | 1    | 1
1     | 2    | 3

I am relatively new at programming and I cant figure out this MySql query. I need to select x_Id only where ((y_Id = 1 AND z_Id = 1) AND (y_Id = 2 AND z_Id = 3)). Therefore, using these numbers as an example the only thing that should be selected is (x_Id =) 1.

**All of these columns are in the same table

The closest I have come is by using this query:

SELECT 
    * 
FROM 
    `relationships` 
WHERE
    y_id = 1 AND
    z_id = 1

UNION    
SELECT 
    * 
FROM 
    `relationships` 
WHERE
    z_id = 3 AND
    y_id = 2

However, this returns all the x_ids and x_id = 1 again as a duplicate.

**I am using sqlPro and MySql 5

Answer 1

no need to Union.

Updated after seeing comments:

select
*
from relationships T1
INNER JOIN relationshipsT2 on t1.x_Id   = t2.x_Id  where
((T1.y_Id = 1 AND T1.z_Id = 1) AND (T2.y_Id  = 2 AND T2.zz_Id= 3))

also you can only return x_Id instead of *

Answer 2

Updated after seeing comments:

Using an aggregate SUM() you can total up the number of conditions met per value of x_id . If the total is > 1, both conditions are met somewhere in the table.

SELECT DISTINCT x_id FROM (
  SELECT
    x_id,
    SUMCASE WHEN (y_id = 1 AND z_id = 1) OR (z_id = 3 AND y_id = 2) THEN 1 ELSE 0 END) AS hasboth
  FROM relationships
  GROUP BY x_id
  HAVING hasboth > 1
) subq

Answer 3

If you are only interested in the x_id value you can use the query above, but just add DISTINCT and project only the x_id value.

Example:

SELECT 
    DISTINCT x_id 
FROM 
 `relationships` 
WHERE
     y_id = 1 AND z_id = 1

UNION

SELECT 
    DISTINCT x_id 
FROM 
    `relationships` 
WHERE
    z_id = 3 AND y_id = 2

There are few other way how to do it, which are even easier such as use OR in the WHERE clause.