如何正确设置sql请求？

Question

I want to get data from column meta_key - 'artikul' and meta_key='_thumbnail_id' .

What I'm doing wrong?

$sql = "SELECT * FROM wp_postmeta WHERE meta_key='artikul' AND meta_key='_thumbnail_id'";

Answer 1

The WHERE only works on one row. So, the condition is never true.

I think you want:

SELECT post_id
FROM wp_postmeta
WHERE meta_key IN ('artikul', '_thumbnail_id')
GROUP BY post_id
HAVING COUNT(*) = 2;

This returns posts that have the two keys. This assumes that you don't have duplicate key values on a post. If so, then use:

HAVING COUNT(DISTINCT meta_key) = 2

Answer 2

SELECT * FROM wp_postmeta WHERE (meta_key='artikul') OR (meta_key='_thumbnail_id')