php从ids数组中选择多行[复制]

Question

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• Get top n records for each group of grouped results 10 answers

For mysql table, I have 10 rows and 5 (half) of them have post_id of 5 while the other 5 rows have post_id of 234.

I want to choose 2 rows from each post_id based on the date:

This is what I have so far

 $post_ids = $_POST['id'][0];
 $ids      = implode(',', $post_ids); //id's in ',' format

 $query    = "SELECT * FROM $table WHERE post_id in ({$ids}) ORDER by date desc limit 2";   

This only gets first two results that matches one of two ids. Do I need to run foreach function for the each query? Is there another method?

Thanks!

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Answer 1

You can use UNION ALL for this task. Try this:

$query = "( select * from $table where post_id = $ids[0] order by date desc LIMIT 1 ) UNION ALL ( select * from $table where post_id = $ids[1] order by age desc LIMIT 1 )";