Question

Simple MySQL tables with matching ID values across tables:

table 1;
pid, firstname

table 2;
id, pid, property, value

Lets say there is one person entry in table 1:

pid: 1
firstname: fred

For each person there are multiple table 2 entries:

pid: 1
property: likes cats?
value: no

pid: 1
property: eye colour
value: orange

pid: 1
property: favourite food
value: sox

I want to select just two of the many table two entries, say the eye colour and favour food entries for a given person ID. What kind of outer join can achieve this?

SELECT `t1`.name
FROM `table1` AS t1
LEFT JOIN `table2` t2 ON `t1`.pid = `t2`.pid
WHERE `t1`.pid = 1
AND `t2`.property =  'eye colour'

I’m stuck here, how to get two rows from table2 and include favour food also? (Before anyone says it, no I can’t change the structure of this database).

Thanks for reading.

Answer 1

How about something like:

 SELECT t1.name, t2.property, t2.value
 FROM table2 t2
 INNER JOIN table1 t1 ON t1.pid = t2.pid
 WHERE t2.pid = 1
 AND t2.property IN ('eye colour','favourite food')

Or you just wanted the first two however MySQL indexed it:

 SELECT t1.name, t2.property, t2.value
 FROM table2 t2
 INNER JOIN table1 t1 ON t1.pid = t2.pid
 WHERE t2.pid = 1
 LIMIT 2

There’s no real reason to use a LEFT JOIN here, since there should always be an associated pid defined in table1.