Database

table "tasks"
ID - autoincrement PK
sJob - varchar task name

table "tasks_log"
ID - autoincrement PK
JobID - mapped to tasks.ID
dDateTime - date and time task is performed

select Customers.cname as c_id, sum(Products.price*Purchases.quantity) as z
from Purchases
right outer join Customers on (Customers.CID = Purchases.cust)
left outer join Stores on (Stores.SID = Purchases.Stores)
left outer join Products on (Products.SKU = Purchases.prod)
###where Stores.city = "Porto"
group by Customers.cname
order by z desc

Table: Words
Id Name
-- ---- 
1  One
2  Two
3  Three

Table: Letters
Id Letter
-- ---- 
1  A
1  B
1  C
2  A
2  D
3  A
3  C

SELECT DISTINCT Words.Name FROM Words JOIN Letters ON Words.Id=Letters.Id WHERE Letters.Letter='A'
INTERSECT
SELECT DISTINCT Words.Name FROM Words JOIN Letters ON Words.Id=Letters.Id WHERE Letters.Letter='C'
ORDER BY name COLLATE NOCASE

SELECT DISTINCT Words.Name FROM Words 
  INNER JOIN Letters AS L1 ON Words.Id=L1.Id
  INNER JOIN Letters AS L2 ON Words.Id=L2.Id
  WHERE L1.Letter='A' AND L2.Letter='C'
ORDER BY Words.Name COLLATE NOCASE

SELECT DISTINCT Words.Name FROM Words 
  INNER JOIN Letters AS L1 ON Words.Id=L1.Id AND L1.Letter='A'
  INNER JOIN Letters AS L2 ON Words.Id=L2.Id AND L2.Letter='C'
ORDER BY Words.Name COLLATE NOCASE