PHP SQL join table rows as keys [closed] - php

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I was wondering if someone could help me. I have the following two tables:
---Posts----
id | title | content |
544 | Alan | Blah
---Postmeta----
metaid | post_id | meta_key | meta_value
1 | 544 | age | 45
2 | 544 | email | test#hotmail.co.uk
I want to join the two tables by post_id and then display the meta_keys. Something like this
SELECT posts.post_id,
postmeta.age,
postmeta.email,
FROM
posts
JOIN posts
ON posts.post_id = postmeta.post_id
Any help would be much appreciated. Cheers

Answer 1

You need to PIVOT the rows inside the table postmeta into columns, using CASE with MAX as an aggregate function to eliminate NULLs like so:
SELECT p.id, pm.age, pm.email
FROM posts p
JOIN
(
SELECT
post_id,
MAX(CASE WHEN meta_key = 'age' THEN meta_value END) AS age,
MAX(CASE WHEN meta_key = 'email' THEN meta_value END) AS email
FROM postsmeta
GROUP BY post_id
) pm ON p.id = pm.post_id
Here is a Demo in sql fiddle
Note that: You are currently storing all values for age and email in one column of the same data type that would be varchar for example then you have to cast the age values to INT in the query in order to get it like INT if you want to perform some calculations later on, and I left this part for you.

Answer 2

SELECT
posts.id,
postmeta.key,
postmeta.meta_value
FROM
posts
JOIN
postmeta ON posts.id = postmeta.post_id
WHERE
postmeta.key IN ('age', 'email')

Answer 3

it should be like this
SELECT posts.post_id,
postmeta.age,
postmeta.email,
FROM
posts
JOIN postsmeta
ON posts.post_id = postmeta.post_id

Answer 4

SELECT posts.id,
postmeta.age,
postmeta.email,
m.meta_key,
m.meta_value
FROM
posts p
JOIN Postmeta m
ON p.id = m.post_id

Answer 5

Instead of saving meta_key in a new row, try to make your table structure like this
metaid | post_id | age | email
1 | 544 | 45 | test1#hotmail.co.uk
2 | 545 | 51 | test2#hotmail.co.uk
3 | 546 | 20 | test3#hotmail.co.uk
4 | 547 | 26 | test4#hotmail.co.uk
you can add more fields to table structure.
and after that you can make a simple join query, that will save your time and resources to execute the query.
like this
SELECT posts.post_id, postmeta.age, postmeta.email FROM posts JOIN postmeta ON posts.post_id = postmeta.post_id;

Answer 6

Joining twice to the postmeta table:
SELECT p.id,
pm1.meta_value AS age,
pm2.meta_value AS email
FROM
posts AS p
LEFT JOIN
postmeta AS pm1
ON pm1.post_id = p.id
AND pm1.meta_key = 'age'
LEFT JOIN
postmeta AS pm2
ON pm2.post_id = p.id
AND pm2.meta_key = 'email' ;