I have the following tables:
+------+-----------+----------+
| Item | ProcessID | PersonID |
+------+-----------+----------+
| 111 | 33 | 1234567 |
+------+----+------------+
| Item | ID | DelegateID |
+------+----+------------+
| 111 | 1 | 4567894 |
+----------+------+
| PersonID | Name |
+----------+------+
| 1234567 | Jhon |
+----------+------+
| 4567894 | Larry|
and I want to join them like this
+-----------+--------+----------+
| ProcessID | Person | Delegate |
+-----------+--------+----------+
| 33 | Jhon | Larry |
But doing just a simple join doesn't get me there.
SELECT Table1.processid, Persons.name,
(select name from Persons where personid =Table2.delegatepersonid) as delegate
FROM Persons
INNER JOIN Table1 ON Persons.personid = Table1.personid
INNER JOINTable2 ON Table1.item= Table2.item
I think this calls for an alias of the persons table so it can be used in two joins: personid and delegatepersonid:
select P.*, T1.*, T2.*
from persons P
inner join table_1 T1 on P.personid = T1.personid
inner join table_2 T2 on T1.item = T2.item
inner join persons P_del on T2.delegatepersonid = P_del.personid ;
You will have to join to Persons
twice since you are looking for two different personid values.
SELECT
one.processid
, pone.name
, ptwo.name
FROM table1 AS one
INNER JOIN table2 AS two
ON one.item = two.item
INNER JOIN persons as pone
ON pone.personid = one.personid
INNER JOIN persons as ptwo
ON ptwo.personid = two.delegatepersonid
I believe Tracy Zhou's solution may work as well.
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