One table, need multiple values from different rows/tuples
I have tables like:
'profile_values'
userID | fid | value
-------+---------+-------
1 | 3 | joe@gmail.com
1 | 45 | 203-234-2345
3 | 3 | jane@gmail.com
1 | 45 | 123-456-7890
And:
'users'
userID | name
-------+-------
1 | joe
2 | jane
3 | jake
I want 开发者_运维知识库to join them and have one row with two of the values like:
'profile_values'
userID | name | email | phone
-------+-------+----------------+--------------
1 | joe | joe@gmail.com | 203-234-2345
2 | jane | jane@gmail.com | 123-456-7890
I have solved it but it feels clumsy and I want to know if there is a better way to do it. Meaning solutions that are either more readable or faster(optimized) or simply best-practice.
Current solution: multiple tables selected, many conditional statements:
SELECT u.userID AS memberid,
u.name AS first_name,
pv1.value AS fname,
pv2.value as lname
FROM users AS u,
profile_values AS pv1,
profile_values AS pv2,
WHERE u.userID = pv1.userID
AND pv1.fid = 3
AND u.userID = pv2.userID
AND pv2.fid = 45;
Thanks for the help!
It's a typical pivot query:
SELECT u.userid,
u.name,
MAX(CASE WHEN pv.fid = 3 THEN pv.value ELSE NULL END) AS email,
MAX(CASE WHEN pv.fid = 45 THEN pv.value ELSE NULL END) AS phone,
FROM USERS u
JOIN PROFILE_VALUES pv ON pv.userid = u.userid
GROUP BY u.userid, u.name
Add "LEFT" before the "JOIN" if you want to see users who don't have any entries in the PROFILE_VALUES
table.
I didn't say this, which I should have (@OMG Ponies) but I wanted to use this within a MySQL view. And for views to be editable you're not allowed to use aggregate functions and other constraints. So what I had to do whas use the same SQL query as I had described in the initial question.
Hope this helps someone, adding tag for creating views.
精彩评论