MySQL Query - SUM of COUNT from multiple tables - mysql

Question

I have three tables:
customers: id, name
contracts_jewels: id, customer_id, paid, transferred, final_date
contracts_objects: id, customer_id, paid, transferred, final_date
As you see, the structure of the last two tables is the same.
The "paid" and the "transferred" fields contain the value 0 or 1.
What I need is to make a query which should return all the clients (no matter if they have contracts or not), and for each client:
id, name, count_contracts_all, count_contracts_active
where:
count_contracts_all would mean the sum of [SELECT COUNT( * ) FROM
contracts_jewels WHERE customer_id=3 (for example)] and [SELECT
COUNT( * ) FROM contracts_objects WHERE customer_id=3 (for example)]
count_contracts_active would mean the sum of [SELECT COUNT( * ) FROM
contracts_jewels WHERE customer_id=3 AND final_date>=Now() AND paid=0
AND transferred=0] and [SELECT COUNT( * ) FROM contracts_objects WHERE
customer_id=3 AND final_date>=Now() AND paid=0 AND transferred=0]
Any idea? Would you please help me? Thank you!

Answer 1

You can count the contracts separately and then just join them up to the customers:
SELECT
c.id,
COALESCE(oc.active_count,0) + COALESCE(jc.active_count,0) as count_contracts_active,
COALESCE(oc.total_count,0) + COALESCE(jc.total_count,0) as count_contracts_all
FROM customers c
LEFT JOIN (
SELECT
customer_id
COUNT(*) as total_count,
COUNT(IF(final_date>=Now() AND paid=0 AND transferred=0,1,NULL)) as active_count
FROM contracts_jewels
GROUP BY customer_id
) as oc ON oc.customer_id = c.id
LEFT JOIN (
SELECT
customer_id
COUNT(*) as total_count,
COUNT(IF(final_date>=Now() AND paid=0 AND transferred=0,1,NULL)) as active_count
FROM contracts_objects
GROUP BY customer_id
) as jc ON jc.customer_id = c.id

Answer 2

One fast solution I can think of right now is:
SELECT COUNT(`temp_table`.*) FROM (
SELECT * FROM contracts_jewels WHERE customer_id=3 UNION ALL
SELECT * FROM contracts_objects WHERE customer_id=3) AS `temp_table`
AND
SELECT COUNT(`temp_table`.*) FROM (
SELECT * FROM contracts_jewels WHERE customer_id=3 AND final_date>=Now() AND paid=0 AND transferred=0 UNION ALL
SELECT * FROM contracts_objects WHERE customer_id=3 AND final_date>=Now() AND paid=0 AND transferred=0) AS `temp_table`

Answer 3

You can join each of those tables twice and add their corresponding COUNTs in your result:
SELECT
c.id,
(COUNT(cj1.id)+COUNT(co1.id)) AS count_contracts_all,
(COUNT(cj2.id)+COUNT(co2.id)) AS count_contracts_active
FROM
customers c
LEFT OUTER JOIN contracts_jewels cj1 ON c.id = cj1.customer_id
LEFT OUTER JOIN contracts_objects co1 ON c.id = co1.customer_id
LEFT OUTER JOIN contracts_jewels cj2 ON
c.id = cj2.id AND
cj2.final_date >= NOW() AND
cj2.paid = 0 AND
cj2.transferred = 0
LEFT OUTER JOIN contracts_object co2 ON
c.id = co2.id AND
co2.final_date >= NOW() AND
co2.paid = 0 AND
co2.transferred = 0
GROUP BY c.id
Note: I haven't run this, but hopefully it sets you in the right direction.

Answer 4

simple solution:
SELECT SUM(c) FROM (
SELECT COUNT(1) as c FROM `tbl1` where ...
UNION
SELECT COUNT(1) as c FROM tbl2 where ...
UNION
SELECT COUNT(1) as c FROM tbl3 where ...
) al