PHP / MySQL的：多列加入结果到1 PHP行

Question

Please consider this MySQL table structure:

table1:
id,name

table2:
table1_id,type, value

I am trying to get all names in table1 and all corresponding types and their average values in table2. "type" could be 1 of 3 fixed values:

SELECT table1.name ,
AVG(table2.value) as avgvalue,
FROM table1 as table1 
LEFT OUTER JOIN table2 as table2 ON table1.id=table2.table1_id
GROUP BY table1.name,table2.type

Result:

name | type | avgvalue
-----+------+-------
name1| type1| value1
-----+------+-------
name1| type2| value2
-----+------+-------
name2| type1| value2
-----+------+-------

My goal is to list each name and all types/average values in one row in a (HTML-)table, regardless if a type / averagevalue exists or not.

So what I would need is something like:

name | type1| type2 |type 3|
-----+------+---------------
name1|value1| value2|      |
-----+------+-------+------+
name2|value2|       |      |
-----+------+-------+------+

My question: Should I use SQL or php to modify the results in order to list all types for a particular name?

If SQL, how? Is my LEFT OUTER JOIN even the right way?

If PHP, what would be the best practice there?

Thanks for any help

Answer 1

You can use the following technique for generating the pivot table as

select 
t1.name,
max(case when t2.type = 'type1' then t2.value end) as `type1`,
max(case when t2.type = 'type2' then t2.value end) as `type2`,
max(case when t2.type = 'type3' then t2.value end) as `type3`
from table1 t1
left join table2 t2 on t2.table1_id = t1.id
group by t1.name