MYSQL :: Slow Subselect

Getting Rid Of Subselect
I have a table, which -- simplified -- looks like this:

create table access_logs (
session_id varchar(32),
request_uri varchar(32)
);
Each pageview logs the users session-id + the request-uri. Now, to determine how many visitors followed a specific path, I need to select the number of sessions, which have a row including specific request_uri.

This is my own feeble attempt, but I have a feeling that this could be rewritten to get rid of the subselects:

select session_id
from access_logs
where session_id in (select session_id
from access_logs
where request_uri = "landing-page.php")
and session_id in (select session_id
from access_logs
where request_uri = "exit-page.php")
group by session_id;

Getting Around Subselect
My knowledge of SQL is basic so I need some help developing a query. Suppose we have a table called BID where each row is a bid on an item up for auction. The relevant columns are BID_ID which is the primary key, ITEM_ID which identifies the item, and a BID_DATE which records the datetime of the bid.

I would like to find the most recent bid for each distinct ITEM_ID in the table. I've worked out the query below which seems to do the job. However, I need to find a query that will work on a pre-4.1 server which does not support subqueries. Is there a way to re-state this query without using a subselect? Perhaps using some kind of join?

SELECT *
FROM BID, (SELECT ITEM_ID AS IID, max(BID_DATE) as MAXDATE
FROM BID
GROUP BY ITEM_ID) as MAXDATES
WHERE
(ITEM_ID=IID) and (BID_DATE=MAXDATE);

Subselect
I had some SQL calls which worked fine on a v4.1 server and now I've moved to another one which is 4.0.24 and certain subselects no longer work. Is there any basic way to convert statements such as this:

SELECT a.name, (SELECT COUNT(*) FROM table2 AS b WHERE b.id=a.id) as count FROM table1 AS a So that it conforms to the 4.0.x standard?

Subselect
i am trying to remove values from a list menu if the join table
doesnt have keys when a key is selected for instance:

locations
locationID

locations_join
locationID shotlistID

SELECT SQL_NO_CACHE l.locationID , l.location FROM locations l LEFT JOIN
locations_join lj ON l.locationID = lj.locationID WHERE l.locationID NOT IN
(select locationID FROM locations_join WHERE shotlistID IN (5069)) ORDER BY
l.location ASC

so when shotlistID is selected all the keys from the locations_join joined
to the shotlistID would be remove from the locations list please help, i'm
trying to do this in one query saving from getting all the keys into an
array then checking if the values arent in the array when generating the
list. Code:

Subselect
Let's say i got this query:
select user.id, (select count(*) as posts_number from posts where posts.user_id = user.id), and some other fields, and a lot of joins here.Is it any way to *say* to mysql that the current user.id selected, is the one in the subselect ?
(the one from select "user.id" and the one in where ... = "user.id")

Subselect
Unless I'm wrong, here's a way to do a subquery (inner join two tables, then inner join the resulting table with a third table). It takes advantage of the two different ways of expressing an inner join ("INNER JOIN", and "t1, t2 WHERE...") to express two separate inner joins within a single statement.
SELECT p.p_id, v2.v_name FROM t_project p, t_volunteer v INNER JOIN t_volunteer v2 ON p.p_id=v2.p_id WHERE p.p_id=v.p_id AND v.v_name LIKE "%mike%";
Is this a technique that people use often? I couldn't see it documented in my SQL book ("MySQL", by Paul DuBois), even though it seems like a useful technique for what is effectively a subselect.

Subselect
I have been held up long enough on the query time to ask for help. Its basically a subselect that never returns.

SELECT id, it.org_id FROM import_temp3 AS it WHERE it.org_id IN ( SELECT p.org_id FROM join_to_person AS j, person AS p WHERE p.id = j.person_id AND j.value = '15' ORDER BY p.org_id ASC ) ORDER BY it.org_id ASC

If I break it up into 2 seperate

SELECT id, it.org_id FROM import_temp3 AS it WHERE it.org_id = 09238323 ORDER BY it.org_id ASC

SELECT p.org_id FROM join_to_person AS j, person AS p WHERE p.id = j.person_id AND j.value = '15' ORDER BY p.org_id ASC

They both return expected values.

Subselect / AS
SELECT
a.id
(SELECT width, height, filename FROM photos WHERE user_id = a.id LIMIT 0,1) AS (width, height, filename)
FROM users a

ORDER BY a.datestamp DESC

you can see my example, using with AS (example).
How can i extract values from subselects?

Subselect In 4.0.12-max With -- New Option
I was reading the manual and it said that the subselect is only
available in 4.1 or using the 4.0.12 with the mysqld =96new command line
to start it.

But it doesn=92t working!! So I downloaded the 4.1 alpha version with =
the
same problem. The error is:

ERROR 1064: You have an error in your SQL syntax. Check the manual that
corresponds to your MySQL server version for the right syntax to use
near =85.

Any ideas? I need subselect working.

Delete Subselect
I know that MySQL 3.23.nnn did not support a delete subselect, just wondering
what the best/most efficient way to do the following is:

delete from table_a where table_a.column_1 in ( select column_1 from table_b);

Assuming that column_1 is the same data type and size in both table_a and table_b.

Update Self Subselect
I have a log table that creates a row for every page view. I have a field called "flagged" which defaults to 0. I'm trying to update the flagged field to 1 when the ip count is greater then 30... This is what I have but I get the error "You can't specify target table 'ip_log' for update in FROM clause".

UPDATE `ip_log` SET `flagged` = 1
WHERE `ip` IN(
SELECT `ip`
FROM `ip_log`
GROUP BY `ip` HAVING COUNT(*) > 30
)

Subselect Wierdness
I am trying to get 3 active article IDs from the table ARTICLES for a random active feed from table FEEDS. Here is the query I have:

CODEselect AID, a.fid as FID from ARTICLES a where active='Y' and a.fid = (SELECT f.fid FROM FEEDS f where active='Y' ORDER BY RAND() desc limit 1) limit 3;

Subselect With NULL
why don't i get some results for the second query?

mysql> select * from a;
+---+
| b |
+---+
| a |
| b |
+---+

mysql> select * from a where b not in (select NULL from dual);
Empty set (0.00 sec).

Subselect Doesnt Work
i am trying to remove values from a list menu if the join table
doesnt have keys when a key is selected for instance:
locations
locationID

locations_join
locationID shotlistID

SELECT SQL_NO_CACHE l.locationID , l.location FROM locations l LEFT JOIN
locations_join lj ON l.locationID = lj.locationID WHERE l.locationID NOT IN
(select locationID FROM locations_join WHERE shotlistID IN (5069)) ORDER BY
l.location ASC

so when shotlistID is selected all the keys from the locations_join joined
to the shotlistID would be remove from the locations list please help, i'm
trying to do this in one query saving from getting all the keys into an
array then checking if the values arent in the array when generating the
list.

Get Last Records Details With A Subselect?
I have a ticketsystem where each ticket belongs to an user and each user can insert a couple of messages to one ticket. Therefore I have implemented a date field (used as primary key). Now I want to get details from the last entry belongs to a ticketid.

kdn_message:
updated (date)
ticketid (int)
kdnr (int)
detail
state

select * from kdn_message t
where updated in (select max(updated) as updated from kdn_message group by ticketid where ticketid=t.ticketid order by updated desc)

what is wrong i this statement?

Convert A Subselect To Inner Join
I was developing a php/postuke app for a client and I wrote two of my SQL queries with subselects. I found out after I was done that they were pretty much stuck with MySQL 4.0.x for awhile, so I need to revamp my queries to avoid subselects. The query uses three tables:

nuke_gwbt_guild_halls
nuke_gwbt_guild_halls_notes
nuke_gwbt_matches

I am getting all of the fields in the first table, matching the notes id from the second table to a notes id in the first table, and then counting some metrics from the third table to return as fields in the resulting recordset, used for ORDER BY sorting. Here is the working subselect query: Code:

Subselect Doesnt Work
i am trying to remove values from a list menu if the join table d=
oesnt have keys when a key is selected for instance:
locations
locationID

locations_join
locationID shotlistID

SELECT SQL_NO_CACHE l.locationID , l.location FROM locations l LEFT JOIN lo=
cations_join lj ON l.locationID =3D lj.locationID WHERE l.locationID NOT IN=
(select locationID FROM locations_join WHERE shotlistID IN (5069)) ORDER B=
Y l.location ASC

so when shotlistID is selected all the keys from the locations_join joined =
to the shotlistID would be remove from the locations list please help, i'm =
trying to do this in one query saving from getting all the keys into an arr=
ay then checking if the values arent in the array when generating the list.

Subselect/left Join
I have a table like this

| ID | THING | NUMBER |
---------------------------------------------------------------
| 1 | white | 1 |
| 2 | white | 2 |
| 3 | green | 1 |
| 4 | green | 3 |
| 5 | brown | 1 |
| 6 | brown | 4 |

and I want to get just white back if I know two numbers are 1 and 2 or green back if I know the nubmers are 1 and 3.

Its mysql 4.1 so I am allowed subselects or left joins. I am drawing a blank!?

Complex Select (Possible Subselect Needed?)
I have a table, b5_assignment_lookup, that is used elsewhere as a lookup but I'm trying to use the data contained by itself here. The table:

CREATE TABLE b5_assignment_lookup (
as_id int(11) NOT NULL auto_increment,
as_blog int(11) NOT NULL default Ɔ',
as_blogger int(11) NOT NULL default Ɔ',
as_milestone enum('start','finish') NOT NULL default 'start',
as_timestamp timestamp NOT NULL default CURRENT_TIMESTAMP,
PRIMARY KEY (`as_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=222 ;
By running this query, I get the following resultset:

mysql> SELECT * FROM b5_assignment_lookup WHERE as_blog = ྕ' AND as_timestamp <= &#55614;&#57158;-09-30'
+--------+----------+-------------+---------------+---------------------+
| as_id | as_blog | as_blogger | as_milestone | as_timestamp |
+--------+----------+-------------+---------------+---------------------+
| 87 | 89 | 41 | start | 2006-05-01 00:00:00 |
|208 | 89 | 41 | finish| 2006-09-02 11:55:27 |
|209 | 89 | 103 | start | 2006-09-02 11:55:27 |
+--------+----------+-------------+---------------+---------------------+
3 rows in set (0.00 sec)
What we have here is that Blogger 41 began writing on Blog 89 on May 1, and on Sep 2 Blogger 103 took over for Blogger 41.

What I really need to grok is all bloggers who blogged all or a part of a range of dates.

For example, I really want to find out which bloggers blogged on blog 89 for all or part of 2006-09-01 to 2006-09-02.

I use this dataset as an example, but we might have completely different circumstances such as Blogger 20 being replaced on the third day of the date range, being replaced by blogger 29 for 10 days and then quitting due to lack of time and the blog going unmanned for 5 days before Blogger 20 decides to step back in on day 25.

The flags are the start/finish, obviously.

Transform SubSelect In OUTER JOIN
maybe I'm simply to dump but I could not transform this SQL-Statment
which uses a Sub-select and create on that uses an OUTER JOIN ....

Ranking Student Grade? With Subquery/subselect?
I am a mySQL newbie here and have some problem defining the mySQL 4.0.14
or 3.23 SQL to get student grade ranking where tied grade have the same
rank.

I used to set it through MS Access 2002 and use this kind of query:

SELECT nilai.studentNIS, nilai.studenttestmark,
(SELECT COUNT(*) FROM tblStudentGrades
WHERE [studenttestmark]>[Nilai].[studenttestmark];)+1 AS NomorUrut FROM
tblStudentGrades AS nilai ORDER BY nilai.studenttestmark DESC;

I've been looking around mySQL documentation and read that subquery can
be redefined as INNER JOIN or using two SQL statement via variable? I
have no idea on the basics of how to set it out though.

Could one of you please help give a me a sample on how this kind of
query should be done on mySQL? Is it possible to do it in single line?
And without having to use PHP/Perl scripts?

Or maybe I should have approach it differently?

Slow
What generally would be the reason why all my db driven sites are running slowly or even hanging. I am on braodband speed but just changed hosts.

Slow Query
i have this query on a website/webapp that has expanded beyond all expectation. It now takes nearly 30secs to return results from the database

SELECT cl_t.Client_ID, Buyer_1_Title, Buyer_1_Prename,
Buyer_1_Surname, Tel_No, Mob_No, Buyer_2_Title,
Buyer_2_Prename, Buyer_2_Surname, Email_Add,
Price_Max, MAX(activity_t.Date) AS lastcomm
FROM cl_t
INNER JOIN cl_want_t
ON cl_t.Client_ID = cl_want_t.Client_ID
AND Agency_Code ='$agencyloggedincode'
AND Deleted = 'N'
LEFT JOIN activity_t
ON Buy_Sell = 'B'
AND Ref_No = cl_t.Client_ID
WHERE cl_t.Sales_Agent_ID = $agentid
GROUP BY cl_t.Client_ID
ORDER BY $order
The problem is the call to MAX(activity_t.Date) AS lastcomm

activity_t holds all known contact with all known clients and as such is a very large table, the call to search through all of these records and return only the date of the last entry for this client is taking the time. If I remove this from the query I get results in 3 seconds.

I have indexing on activity_t.Date & activity_t.Ref_No

Question, is there a way of doing this quicker within the table I already have, or should I create another table that just holds the last update date for each client, and get the date from this much smaller table.

Slow Authentication
MySQL V 5.0.18 on SUSE 10.1

I'm not a complete *nix noob, but I sure as hell ain't a *nix or MySQL pro.

This is a new installation. Everything screaming fast. Unless it deals w/authentication.

Try to get in w/SQLyog from W2K locally ... intitial connection takes ~20 seconds. Then everything screaming fast.

Web Server (W03) attempts to connect via MyODBC ... same result ... initial connection takes ~20 seconds. Subsequent queries screaming fast.

VNC into the box at any time ... everything fast. (would seem to eliminate network/connection issues)

Why Is This Query Too Slow?
I find this query to be exceptionally slow(around 2.5 seconds), could some tell me why this is so?

MySQL
SELECT st.profile_views,count( DISTINCT p.ID ) news_submitted, count( DISTINCT pv.ID ) news_voted, count( DISTINCT pcom.ID ) news_commented, u.joined, u.weight FROM users u LEFT JOIN posts p ON p.submitted_user_id = u.user_id LEFT JOIN post_votes pv ON pv.user_id = u.user_id LEFT JOIN post_comments pcom ON pcom.user_id = u.user_id LEFT JOIN stats st ON st.user_id=u.user_id WHERE u.user_id='john' GROUP BY u.user_id
I traced the cause to this line
count( DISTINCT p.ID ) news_submitted (from LEFT JOIN posts p ON p.submitted_user_id=u.user_id)
But when i execute something like this

MySQL
SELECT count( DISTINCT p.ID ) news_submitted FROM posts WHERE submitted_user_id='john'
it is quite fast (around 0.03 seconds)
So why does it slow down when i'm joining the above query with 3 other tables ?
Should i use INTEGER for user_id instead of string like 'john'?

Slow Query Log
my slow log is catching a slow query, however the timestamp for the query is "0". I also placed a timestamp on the query to echo out to the results page, and it is about 4 thousands of a second. Why is it showing in the slow log?

Slow Query Using NOT IN
I am migrating a MSSQL server to MySQL. I know the following SQL is valid for both servers, but MSSQL finishes execution of the query almost instantly, and MySQL has been running the query for the past ten minutes and still is not finished. There is basically the same amount of data in each database. Does anyone know ....

Update Too Slow
I need to update 25 * 5000 records, if I do one at the time it takes too
long time, do any one have a good proposal ?

MySQL Slow
I had downloaded a few years back mySQL v3.51 installed but never used it. Now I wanted to convert some B-TREE databases to mySQL and did some testing via ODBC to insert 70,000 records: My results:

MS ACCESS: ~60,000 msecs
MYSQL v3.51 ~18,000 msecs

Impressed with the speed, I went ahead and got the latest MySQL v5.1. Uninstalled the older version, I had nothing there to preserve, so I did a simple new install with MySQL v5.1. I noticed the size of the files and BINEXE increasted by 1,000,000%. Ok, Bulky. Not a problem.

I reran the same ODBC test, and now I got:

MYSQL v5.1: ~450,000 msecs or 7.5 freaking MINUTES!

What the hell happen? Nothing was done. I'm knew to MYSQL. I just installed it with all the defaults. I did choose "developer's machine" for the "optimizer wizard"

I can't redistribute MYSQL v3.51 and force it down people's throats! I have to use what they are using already, if already installed. Not even my current system takes 1 minute to add 70,000 records. Why 7.5 minutes? All it is simple inserts/free statements.

Join Too Slow
I'm creating a query that use Join clause. I tested it in MySQL 4.0.24 and with MS-ACCESS. . . . in MySQL is slow!!! any suggestion ?

Slow Connection
I build an application and installed it on many machines. In every machine except two, the program works without problems. On this two, the connection with database is too slow.

I saw the opened doors with 'netstat' and the computer opens about 5 or 6 ports (to the port 3306 of the mysql server) before sucessfuly connect with MySql Database and execute the sql. I don't know what could be happening. I realy need to fix this because the progrm is too slow with this error. Could anyone know what could be happening??

Slow Connect
Does anybody know why it sometimes takes more than 10 seconds to connect to a database and sometimes it just takes half a millisecond?

Slow Queries
I had a working web page that queried 20 tables and returned the data in the form of a table ... all of a sudden this stopped returning the results , and on investigation, up to ten tables, the query time is about 0.01 second ... but as the number of tables is increased to fifteen, the query time increases to 60 second .. and then gets too slow with nothing being returned at all.

A few days ago, this was all working fine. There have been no changes to the code on the web page ....
The version of mysql is 4.0.20, the server is a dual 1 MHz Xeon with 512 meg of RAM, running linux.

The tables have up to 15 fields each, and there is only simple text or numerical values in the fields.

Can anyone suggest what might have changed to suddenly slow down the query ?

Slow UPDATE
I have a table with the following structure;

CREATE TABLE my_table
(
id_1 int(11) NOT NULL ,
id_2 int(10) NOT NULL ,
stauts tinyint(1) NOT NULL DEFAULT 0 ,
PRIMARY KEY (id_1)
) Engine =InnoDB';

The table currently has arround 100,000 entries. When I try to run variations of the following statement it is taking around 4 seconds per query;

UPDATE IGNORE my_table
SET id_1 = 74240, id_2 = 5

I need it to be running a lot faster than 4 seconds per query as I need to update upwards of 100,000 records a day! My server is fairly beefy, a 3 gig dual core opeteron and is generaly running below 1.0 load.

MySQL Very Slow.
I have this one site that slows down all my others because the queries are so massive.

For example one of these queries I use to-do a search by a user's account number. I also get the position he is at on the list, and in order to-do that I need to select ALL the rows.

For example, I filter out the other queries in php.
CODE$num = 1;
$q = mysql_query('SELECT * FROM lists');
while($r = mysql_fetch_assoc($q))
{

   if($r['account']=='accountNum')
   {
         print 'You are at pos. num '.$num.'<br>';
   }
   $num++;
}

Why Does MySQL So Slow
I just changed to use MySQL few days ago but it was a bad idea. My server now is running very slowly with the database. I'm using Perl5 and DBD::Mysql in my script. The system is Linux9, Apache2.

I looked at these mysql pid and saw a lot of activities (about 400) while there are more 100 users online at this moment and lots of running under a the same pid number.

What Causes Slow Queries
What causes periodic slow queries? I have checked my slow query logs and for some reason everyonce in awhile, a query thats never slow might be for example, one took 3 seconds to execute and every once in awhile a chat might take 10 seconds of cpu time while rest of the time 0.09...why is it it flexuates so much?

Very Slow Select
The line indicated below from my php script is very slow (about 10 seconds). I have this field indexed so I thought that it would be much faster. Could someone tell me what might be wrong?

I'm also including the dump of the table definitions. This is a cd cataloging database.

Right now the filenames table is empty and I'm trying to populate it, but at the rate it's going it would take days. I have about 700,000 records in the 'files' table, but none in the 'filenames' table yet. Code:

Slow Running Sql
i am not using mysql but an unknown database system on a unix box - i have no control over the database but have purchased an odbc driver that seems very 'clunky' after using mysql - this is an sql statement question rather than a mysql tech question. if i run this:

SELECT
MK_01_vehicleRecords.registrationnumber, MK_01_VehicleRecords.vehiclenumber
FROM MK_01_VehicleRecords
WHERE (MK_01_VehicleRecords.vehiclenumber = '36176')

Slow Connections
I am using MyODBC-3.51.11-2-win on Win 2003 OS. I am not able to see all of the connections in the list under the System DSN tab. The connections that show allow the ASP pages to run at an expected rate.

However, the ones not showing in the list are running extremely slow. If I attpemt to recreate the connection I am told that the connection already exists and asks if I want to replace the existing connection. Wheter I click yes or no the connections do not show and the pages run slowly. How do I get them to show or resolve the issue. The ASP code is the exact same SQL statements and connection strings as the in previous applications.

Slow Restore
Mysql 4.1.15 on Win2k. Using InnoDB.

Using the mysql administrator gui to create a backup, everything goes
fine, and restores quickly.

Using the command line:

mysqldump %dbname% --single-transaction > %dbname%.sql

creates a file about 15% smaller than the gui produces, and is
EXTREMELY slow to restore. I have tried adding locks, skip opt,
everything. What does the gui use for a command to create this dump?

Slow Queries
I just got a new dual opteron system, with raid 01, 2gb ram, and fedora
core linux running 2.4.22-smp kernel. For some reason mysql is running
pathetically slow.

Queries that should take 2ms occasionally take up to
20 seconds. It isn't every time, but almost once per page. The problem
usually occurs with queries accessing the large tables (up to 1gb), but
not always. I've tried 2 versions I compiled myself (with flags
suggested in the readme), as well as the version off the mysql website.
All were 4.0.18, and all had the problem.

Slow Query
I have a query that is running really slow !!!!
I have joined on Key fields and indexed the tables fully but it is still solw.
--------------------------------------------

select d.id, a.signed, u.Forename, u.Surname, d.paid, p.date, d.payment, p.amount, d.acctual
from details d
join poten a
on a.id = d.id
left join recieved p
on d.id = p.id
left join users u
on a.signed = u.userid
where d.paid > '01-Dec-2005'
and d.authorrceived is not null
and d.authorrefused is null
and ((d.payment starting 'E' or
d.payment starting 'e') or
(d.payment starting 'Q' or
d.payment starting 'q' and
p.target = '500'))
order by d.paid, a.signed, d.id

HEAP So Slow
I have a heap database, with 1.5-1.6 milion rows. on that is 2 columns...

ID | Title

title is indexed. When i run a query like this
------------------
SELECT index_data.* FROM index_data INNER JOIN `index` ON index_data.id=index.id AND index.title LIKE '%$query%' WHERE playtime > $dur... The execution time is about seconds...
------------------
Even a single like statement just on `index` (heap) takes 3-6 seconds.

Here's the table stats...
----------------------------
Data 397,442 KB
Index 24,639 KB
Total 422,081 KB
----------------------------
Why??

MySQL Slow Log
I have the long query time set to 15 yet MySQL is still showing results with a query time of 0 in the slow query log.

It says enter time in "seconds" in the MySQL Administrator but did it mean in milliseconds??

Slow Subquery
Can anyone tell me why the following query with sub-query takes forever to finish? (I've le it run for 20 minutes, and it still hasn't finished)

select date from temps where date in (select distinct date from observations where camera like "a")

The sub query returns 10 dates. The outer query is on a table that contains about 40,000 rows. What's the big deal here? All I'm trying to do is select rows from "temps" that match a small range of 10 dates. Is there another way to do this? Is a sub-query the wrong approach?

Slow Db Access
I have worked with a few mysql dbs on different servers but i have recently been asked to work with one on nicnames. It seems horribly slow. Working in phpMyAdmin (which i had to install myself) it takes ages when i want to do anything. View the table structure, view the data..etc. Any way i can test the speed so that i can compare it against another server i work with and proove there is a speed issue and take it to nicnames cus it is crazy and is going to affect the speed of the website!!

Slow Performance
On my index.php page, I have a simple query that checks the session_id against a table where I store other session_id'. If it's not there, it records it (unique hit). If it's there, it doesn't record it (not a unique hit.) This usually goes off without a hitch, and every month or so I empty the table.

Right now I only have about 2500 rows, and it's taking forever to load the page. Is there something possibly server related that could be causing this? My host charges an arm and a leg just to see if there's something wrong if I bring up an issue, so I'd like some insight as to whether there's a commonly known server-side issue that can bog down performance.