Get total cost for a customer call - mysql

Question

I have 2 tables = customer and their call history
Now I want to charge them based on call duration and that too for a specific month say Jan 2015.
Here is the criteria to calculate the cost for calls -
A) For incoming calls, the charge is 1 unit per second. Example if the duration is 250 seconds then cost is 250
B) For outgoing calls, for the first 2mins, the cost is fixed at 500 units. for subsequent seconds the cost is 2 units per second.
Example if the outgoing duration is 5mins then cost is 500 units + 2*3*60 units = 860 units
Below are the tables:
customer table with columns id, name, phone
history table with columns id, incoming_phone, outgoing_phone, duration, dialed_on (YYYY-MM-DD)
I have come up with below queries for my conditions:
For incoming call cost:
select c.name, c.phone, h.duration as cost
from customer c join history h on c.phone = h.incoming_phone
When I run the above query I did not get any syntax errors.
For outgoing call cost:
select c.name, c.phone, CASE
WHEN h.duration > 120 THEN 500 + 2*(h.duration-120)
ELSE 2*(h.duration-120)
END; as cost
from customer c join history h on c.phone = h.outgoing_phone
When I run the above query I got syntax error like "ERROR 1109 (42S02) at line 1: Unknown table 'c' in field list"
I want to join these two queries and get the total cost and display the fields as name, phone, cost
I still need to add a condition for a specific month to restrict data for Jan 2015, but got stuck with the approach.

Answer 1

The error is due to the extra semicolon ; after END.
Sounds like your final query will be this:
SELECT c.name,
c.phone,
SUM(CASE WHEN h.direction = 'in' THEN h.duration END) as IncomingCost,
SUM(CASE WHEN h.direction = 'out' AND h.duration > 120 THEN 500 + 2*(h.duration-120)
WHEN h.direction = 'out' AND h.duration <= 120 THEN 500
END) as OutgoingCost,
SUM(CASE WHEN h.direction = 'in' THEN h.duration END +
CASE WHEN h.direction = 'out' AND h.duration > 120 THEN 500 + 2*(h.duration-120)
WHEN h.direction = 'out' AND h.duration <= 120 THEN 500
END) as TotalCost
FROM customer c
JOIN (SELECT 'out' as directon, duration, dialed_on, outgoing_phone as phone
FROM history
WHERE YEAR(dialed_on) = 1995
AND MONTH(dialed_on) = 1
UNION ALL
SELECT 'in' as direction, duration, dialed_on, incoming_phone as phone
FROM history
WHERE YEAR(dialed_on) = 1995
AND MONTH(dialed_on) = 1
) h ON c.phone = h.phone
GROUP BY c.name,
c.phone