Re: Query Problem

[Roland Bouman]

Ok, all these queries need a join:

SELECT t2.name
, t2.surname
, t1.data
FROM table2 as t2
INNER JOIN table1 as t1
ON t2.clientid = t1.clientid

This gets all corresponding combinations of records from both tables. For each of your cases, you need to filter out those rows that interest you. If you MySQL version supports subqueries (>=4.1), you can do this like so:

SELECT t2.name
, t2.surname
, t1.data
FROM table2 as t2
INNER JOIN table1 as t1
ON t2.clientid = t1.clientid
WHERE t2.datebegin = (
SELECT min(t.datebegin)
FROM table2 as t
WHERE t.clientid = t2.clientid
)
So, we added a WHERE that requires that the datebegin of our joined table2 t2 equals the minimum databegin in table2 for that client. This would take query of query 1. To solve query 2, simply substitute max(t.datebegin) instead of min(t.datebegin). For the third query, its similar, but instead of comparing dates you must compare the difference of two dates:

SELECT t2.name
, t2.surname
, t1.data
FROM table2 as t2
INNER JOIN table1 as t1
ON t2.clientid = t1.clientid
WHERE t2.dateend- t2.datebegin = (
SELECT min(t.dateend- t.datebegin)
FROM table2 as t
WHERE t.clientid = t2.clientid
)