DISTINCT and RND() on joined tables - php

Question

I’m really struggling with how to write a query which randomly selects 50 DISTINCT random titles from one table in my MySQL database and then selects 1 random excerpt from each title from a separate table. The first table is titles and the second is excerpts.
I’ve tried two queries nested together but this either doesn’t work or returns duplicate titles despite supposedly being DISTINCT.
Could somebody please, PLEASE help me with where I’m going wrong?!
My existing PHP:
$distincttitlequery = “SELECT DISTINCT titleid FROM titles ORDER BY rand() LIMIT 50”;
$distincttitleresult = mysql_query($cxn,$distincttitlequery);
while ($distinctqueryreturn = mysqli_fetch_assoc($distincttitlequery))
{
extract ($distinctqueryreturn);
$selectedtitle = $titleid;
$randomexcerptquery = “SELECT excerpts.titleid, excerpts.excerptid, excerpts.excerptsynopsis, title.titleid, title.title FROM excerpts INNER JOIN titles ON excerpts.titleid=title.titleid WHERE titleid = ‘$selectedtitle’ ORDER BY rand() LIMIT 1”;
$randomexcerptresults = mysql_query($cxn,$randomexcerptquery);
while ($randomexcerptreturn = mysqli_fetch_assoc($randomexcerptquery))
{
[ECHO RESULTS HERE]
}};
I’ve read in similar posts about GROUP BY but I need to create a query which deals with distinct, random and joined tables and I have absolutely no idea where to start!
My existing code uses DISTINCT on multiple columns and joins the tables but this leads to titles being repeated in returned results. I can LIVE with that but I’d love to perfect it!
Thank you in advance for your help with this.

Answer 1

In mysql 8 you can use row_number to get 1 random row per titleid
SELECT
titleid,title,excerptid,excerptsynopsis
FROM (
SELECT
e.titleid, e.excerptid, e.excerptsynopsis
,ROW_NUMBER() OVER( PARTITION BY e.titleid ORDER BY rand()) rn
, t.title
FROM excerpts e
INNER JOIN (SELECT DISTINCT titleid FROM titles ORDER BY rand() LIMIT 50) t ON e.titleid=t.titleid
) t1
WHERE rn = 1