SQL - joining rows from same table
I only know the bare min when it comes to SQL so please treat me as a complete noob!
I have a table which has many rows but some of them can pair up by the id and I want return array of those rows merged.
post_id # meta_name # meta_value #
======================================
1 # bar # 44 #
1 # foo # on #
2 # bar # 1 #
2 # foo # on #
3 # bar # 1 #
3 # foo # off #
as a scaled down version, imagine the above of my table and I am aiming to return 2 results of
1 # foo # bar # 44 # on
2 # foo # bar # 开发者_如何学Python 1 # on
based on that the ids are related and that c2 has the value of 'on'
my attempt was the following from some reading but not getting anywhere
SELECT
t1.post_id, t2.post_id, t1.meta_name, t2.meta_name, t1.meta_value, t2.meta_value
FROM
`ecom_page_meta` t1
JOIN
`ecom_page_meta` t2
ON
t1.post_id = t2.post_id
WHERE
t1.meta_name = 'featured-products'
AND
t1.meta_value = 'on'
any help would be muchly appreciated
** EDIT **
I thought Id just post the syntax which worked nicely below thanks to the answer below:
SELECT L.post_id, L.meta_name, R.meta_name, L.meta_value, R.meta_value
FROM `ecom_page_meta` L
INNER JOIN ecom_page_meta R
ON L.post_id = R.post_id
AND L.meta_name = 'featured-products-order'
AND R.meta_value = 'on'
WHERE R.meta_name = 'featured-products'
ORDER BY L.meta_value
DESC
THanks again.
Create test data:
SQL> create table ecom_page_meta (post_id number not null
2 , meta_name varchar2(15) not null
3 , meta_value varchar2(15) not null);
Table created.
SQL> insert into ecom_page_meta values (1, 'bar', '44');
1 row created.
SQL> insert into ecom_page_meta values (1, 'foo', 'on');
1 row created.
SQL> insert into ecom_page_meta values (2, 'bar', '1');
1 row created.
SQL> insert into ecom_page_meta values (2, 'foo', 'on');
1 row created.
SQL> insert into ecom_page_meta values (3, 'bar', '1');
1 row created.
SQL> insert into ecom_page_meta values (3, 'foo', 'off');
1 row created.
SQL> commit;
Commit complete.
Query to give results matching OP's sample:
SQL> select L.post_id, L.meta_name, R.meta_name, L.meta_value, R.meta_value
2 from ecom_page_meta L
3 inner join ecom_page_meta R
4 on L.post_id = R.post_id
5 and L.meta_value <> 'on'
6 and R.meta_value = 'on'
7 where L.meta_name = 'bar';
POST_ID META_NAME META_NAME META_VALUE META_VALUE
---------- --------------- --------------- --------------- ---------------
1 bar foo 44 on
2 bar foo 1 on
I still do not know what WHERE t1.meta_name = 'featured-products'
has do to do with anything since no sample data includes t1.meta_name of the string 'featured-products'.
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