Synay :
I need help with a mysql query. I have these two tables in my database.
ZONE
+----+--------+
| id | name |
+----+--------+
| 1 | ZONE 1 |
| 2 | ZONE 2 |
| 3 | ZONE 3 |
+----+--------+
DISTRICT
+----+---------+--------+-------------------+
| id | id_zone | name | number_voters |
+----+---------+--------+-------------------+
| 1 | 1 | DIST 1 | 2000 |
| 2 | 1 | DIST 2 | 3000 |
| 3 | 1 | DIST 3 | 4000 |
| 4 | 2 | DIST 4 | 3500 |
| 5 | 3 | DIST 5 | 1400 |
| 6 | 3 | DIST 6 | 3800 |
+----+---------+--------+-------------------+
When I make a two select and union with conditions
SELECT z.`name`, sum(d.`number_voters`) AS quantity
FROM zone z
JOIN district d
WHERE z.`id`= d.`id_zone`
AND z.`id`=1
GROUP BY z.`name`
UNION
SELECT d.`name`, d.`number_voters`
FROM zona z
JOIN district d
WHERE z.`id`= d.`id_zone`
AND d.`id_zone`=1;
It shows me how I want:
+--------+----------+
| name | quantity |
+--------+----------+
| ZONE 1 | 9000 |
| DIST 1 | 2000 |
| DIST 2 | 3000 |
| DIST 3 | 4000 |
+--------+----------+
Here comes the problem by removing the id from the both of query, it shows them like this:
+--------+----------+
| name | quantity |
+--------+----------+
| ZONE 1 | 9000 |
| ZONE 2 | 3500 |
| ZONE 3 | 5200 |
| DIST 1 | 2000 |
| DIST 2 | 3000 |
| DIST 3 | 4000 |
| DIST 4 | 3500 |
| DIST 5 | 1400 |
| DIST 6 | 3800 |
+--------+----------+
I need you to show me this way:
+--------+----------+
| name | quantity |
+--------+----------+
| ZONE 1 | 9000 |
| DIST 1 | 2000 |
| DIST 2 | 3000 |
| DIST 3 | 4000 |
| ZONE 2 | 3500 |
| DIST 4 | 3500 |
| ZONE 3 | 5200 |
| DIST 5 | 1400 |
| DIST 6 | 3800 |
+--------+----------+
I don't know why, or if it´s possible to do, your help would be very helpful.
forpas :
Use a type column indicating that the row is a zone or a district and sort 1st by the zone's id and then by type, name:
SELECT name, quantity
FROM (
SELECT 1 type, z.id, z.name, sum(d.number_voters) AS quantity
FROM ZONE z JOIN DISTRICT d
ON z.id= d.id_zone
GROUP BY z.id, z.name
UNION ALL
SELECT 2 type, d.id_zone, d.name, d.number_voters
FROM DISTRICT d
) t
ORDER BY id, type, name
Unless there are districts that don't belong to any zone you don't need a join in the 2nd query of UNION.
See the demo.
Results:
| name | quantity |
| ------ | -------- |
| ZONE 1 | 9000 |
| DIST 1 | 2000 |
| DIST 2 | 3000 |
| DIST 3 | 4000 |
| ZONE 2 | 3500 |
| DIST 4 | 3500 |
| ZONE 3 | 5200 |
| DIST 5 | 1400 |
| DIST 6 | 3800 |