Does anybody have any ideas how I can get around a #1235 - This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery' error?
My query is below ( I've read that I can upgrade mysql but this isn't possible):
$query = #mysql_query("SELECT * FROM posts
WHERE postid NOT IN
( SELECT postid FROM log
ORDER BY posted DESC
LIMIT 10)
ORDER BY (RAND() * Multiplier)
LIMIT 1");
According to this bug, you can use this ugly workaround:
SELECT * FROM t1 WHERE s1 NOT IN
(SELECT * FROM (SELECT s2 FROM t2 ORDER BY s1 LIMIT 1) AS alias)
You can rewrite your query using JOIN:
SELECT *
FROM posts NATURAL LEFT JOIN (
SELECT postid FROM log ORDER BY posted DESC LIMIT 10
) t
WHERE t.postid IS NULL
ORDER BY RAND()
LIMIT 1
Be aware, however, that ORDER BY RAND() is very expensive. Not only must a random value be calculated for each record, but then a sort must be performed on the results. Indexes are of no use.
You would fare better if you had a column col containing unique integers, then with an index on col you can very rapidly obtain a random record with:
SELECT *
FROM posts NATURAL LEFT JOIN (
SELECT postid FROM log ORDER BY posted DESC LIMIT 10
) t JOIN (
SELECT RAND() * MAX(col) AS rand FROM posts
) r ON posts.col >= r.rand
WHERE t.postid IS NULL
LIMIT 1
Note that the uniformity of such "randomness" will depend on the distribution of the integers within col after any other filtering has taken place.
Related
I am using this MySQL query. It takes 6.3 seconds or more time.
SELECT * FROM `wp_wpds_tlds` WHERE 1 AND `id` IN (SELECT p.`tld_id` id FROM `wp_wpds_category_pivot` p, `wp_wpds_categories` c WHERE c.id=p.category_id AND `category` LIKE '%City%') ORDER BY `tld` ASC
You have to remove 1 AND after WHERE:
SELECT * FROM wp_wpds_tlds WHERE id IN (SELECT p.tld_idid FROMwp_wpds_category_pivotp,wp_wpds_categoriesc WHERE c.id=p.category_id ANDcategoryLIKE '%City%') ORDER BYtld` ASC
I have a set of tracks that need to be played,
There are something like 70 tracks in the database, and my script need to generate a new ID to play in order to start the next track.
Current query: ($row['v_artist'] is the current artist playing)
SELECT *
FROM t_tracks
WHERE v_artist NOT LIKE '%".$row['v_artist']."%'
ORDER BY RAND()
LIMIT 1;
Now I wish to add a subquery to rand() so that it picks a random id, but not from the first 50 (NOT IN?)
Subquery:
SELECT *
FROM `t_playlist`
ORDER BY pl_last_played DESC
LIMIT 50, 1
How can I get a random ID from t_tracks that does not exist in the query for t_playlist?
Conceptually, I think you want this:
SELECT *
FROM t_tracks
WHERE v_artist NOT LIKE '%".$row['v_artist']."%' AND
track_id NOT IN (SELECT track_id FROM t_playlist ORDER BY pl_last_played DESC LIMIT 50)
ORDER BY RAND()
LIMIT 1;
However, MySQL doesn't permit LIMIT in some subqueries, so use LEFT JOIN instead:
SELECT t.*
FROM t_tracks t LEFT JOIN
(SELECT track_id
FROM t_playlist
ORDER BY pl_last_played DESC
LIMIT 50
) p
ON t.track_id = p.track_id
WHERE t.v_artist NOT LIKE '%".$row['v_artist']."%' AND
p.track_id IS NULL
ORDER BY RAND()
LIMIT 1;
Here is my query:
SELECT * FROM Photos WHERE Event_ID IN ($eventidstring)
I know I can limit the total amount of results from this query using LIMIT 5
I need the Limit the amount of results Per value in $eventidstring.
So if $eventidstring = 23,41,23*
*And there are 10 results WHERE Event_ID = 23, I want to limit this amount to 5. The same for all the other values in $eventidstring.
You may have some joy doing something similar to Oracle's RANK by PARITION in MySQL.
Sadly this feature is not available in MySQL though you can work around it using this method
Dump that in an inline view and then select those rows with rank <= 5;
Hence:
SELECT t.* FROM (
SELECT (
CASE Event_id
WHEN #curEventId
THEN #curRow := #curRow + 1
ELSE #curRow := 1 AND #curEventId := Event_Id END
) AS rank,
p.*
FROM Photos p INNER JOIN (SELECT #curRow := 0, #curEventId := '') r
ORDER BY p.Event_Id DESC
) t
WHERE t.rank <= 5 ORDER BY t.Event_Id asc;
Consider how you are going to 'choose' the top five by Event_Id too. You can always add in more after the ORDER BY p.Event_Id DESC to decide this.
I take it you're writing that query somewhere inside your PHP, so you need to split the $eventidstring into it's component values, form a SELECT for each and UNION all after the first one.
You sould do this with a loop of some sort, and concatenate the query strings in the loop...
If I understand correctly and you want to get five of each, you can use this:
(SELECT * FROM Photos WHERE Event_ID = 23 LIMIT 5)
UNION
(SELECT * FROM Photos WHERE Event_ID = 41 LIMIT 5)
UNION
(SELECT * FROM Photos WHERE Event_ID = ... LIMIT 5)
...
Maybe with a SELECT UNION but you need a new select for each value:
SELECT * FROM Photos WHERE Event_ID = 23 LIMIT 5
UNION SELECT * FROM Photos WHERE Event_ID = 41 LIMIT 5
UNION SELECT ...
Using PHP and MySQL, is there a way to use a different ORDER BY for each of the SELECT statements in a UNION?
SELECT * FROM the_table WHERE color = 'blue' ORDER BY price ASC LIMIT 5
UNION ALL
SELECT * FROM the_table WHERE color = 'red' ORDER BY RAND() LIMIT 10
The above statement does not work. It seems you can only do an ORDER BY on the final result set. Is there a way to do an ORDER BY on the first SELECT then a different ORDER BY on the second SELECT using UNION?
(SELECT * FROM the_table WHERE color = 'blue' ORDER BY price ASC LIMIT 5)
UNION ALL
(SELECT * FROM the_table WHERE color = 'red' ORDER BY RAND() LIMIT 10)
Please note that this does not work if you don't specify a LIMIT (though you can specify a very large dummy limit). See mysql documentation (13.2.7.3. UNION Syntax):
"Use of ORDER BY for individual SELECT statements implies nothing about the order in which the rows appear in the final result because UNION by default produces an unordered set of rows...
"To cause rows in a UNION result to consist of the sets of rows retrieved by each SELECT one after the other, select an additional column in each SELECT to use as a sort column and add an ORDER BY following the last SELECT:
"(SELECT 1 AS sort_col, col1a, col1b, ... FROM t1)
UNION
(SELECT 2, col2a, col2b, ... FROM t2) ORDER BY sort_col;
To additionally maintain sort order within individual SELECT results, add a secondary column to the ORDER BY clause:
"(SELECT 1 AS sort_col, col1a, col1b, ... FROM t1)
UNION
(SELECT 2, col2a, col2b, ... FROM t2) ORDER BY sort_col, col1a;"
This SQL query gives me the results I want; however, I want the results ordered by a different column:
SELECT *
FROM post
INNER JOIN account ON post.account_id = account.account_id
WHERE post_id > new
ORDER BY post_date
ASC LIMIT 10;
I can not simply change ORDER BY post_date ASC to ORDER BY post_id DESC, while that will in fact order the query the way I want it... it will give me the wrong 10 posts.
I simply want to take the EXACT RESULTS of the above query then reorder the results by the post_id.
I would like to do this with SQL if possible, if not I could order the results by adding the results into a new array reversed.
Use a subquery to reorder:
SELECT * FROM (
SELECT *
FROM post
INNER JOIN account ON post.account_id = account.account_id
WHERE post_id > neww
ORDER BY post_date ASC LIMIT 10;
) ORDER BY post_id
Use a subquery:
SELECT * FROM (
SELECT *
FROM post
INNER JOIN account
ON post.account_id = account.account_id
WHERE post_id > neww
ORDER BY post_date ASC
LIMIT 10) AS T1
ORDER BY post_id DESC