Mysql very slow subquery optimizing

Mysql very slow subquery optimizing

By : Elias Salom
Date : November 17 2020, 11:55 AM
I hope this helps you . Assuming that (movie_id,category_id) is unique in movies_categories table, I'd get the specified result using join operations, rather than subqueries.
To exclude "skipped" movies, an anti-join pattern would suffice... that's a left outer join to find matching rows in skipped_movies, and then a predicate in the WHERE clause to exclude any matches found, leaving only rows that didn't have a match.
code :
  FROM movies m
  JOIN movie_categories c 
    ON c.movie_id = m.id 
   AND c.category_id = 1
  JOIN skipped_movies s
    ON s.movie_id = m.id
   AND s.user_id = 1
 WHERE s.movie_id IS NULL
   AND m.score <= 9
    BY m.score DESC
... ON movie_categories (category_id, movie_id)
... ON skipped_movies (user_id, movie_id)

Share : facebook icon twitter icon
MySql select from subquery slow (even though subquery on it's own is fast)

MySql select from subquery slow (even though subquery on it's own is fast)

By : Piercing Light
Date : March 29 2020, 07:55 AM
I hope this helps . MySQL buffers the inline view before doing any operations on it.
0.0006 seconds you see for the first query is most probably the response time (the first row fetched), not the overall time (the last row fetched).
code :
order_item (order_id, checked)
order_item (order_id, last_update)
FROM    order o
WHERE   o.canceled = 0
        o.return_date > '2011-03-14'
        SELECT  MIN(checked)
        FROM    order_item oi
        WHERE   order_id = o.id
        ) = 0
        SELECT  MAX(last_update)
        FROM    order_item oi
        WHERE   oi.order_id = o.id
        ) > '2011-03-14'
Optimizing MySQL subquery

Optimizing MySQL subquery

By : user3756418
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , Working with MTA API.
code :
select trip_id 
from stop_times 
where stop_id in (111, 222)
group by trip_id
having count(distinct stop_id) = 2
MySQL, Optimizing Subquery

MySQL, Optimizing Subquery

By : Dj 2nyi
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , Strugle with optimizing this subquery that count item:
code :
   `tblScan`.`crewId` AS `crewid`
   COUNT(`tblScan`.`id`) AS `number_documents`,
   SUM(IF(`tblScan`.`classification` IS NOT NULL,1,0)) AS `classified`,
   SUM(IF(`tblScan`.`classification` IS NULL,1,0)) AS `unclassified`,
   CONCAT(`tblcrew`.`name`, ' ', `tblcrew`.`surname`) AS `crewname`,
   MAX(`tblScan`.`uploadeddate`) AS `uploadeddate`,
   MAX(`tblScan`.`uploadedby`) AS `uploadedby`,
   MAX(IFNULL(`tblScan`.`updateddate`,'0000-01-01')) AS `updateddate`,
   MAX(IFNULL(`tblScan`.`updatedby`,'0')) AS `updatedby`
FROM tblScan
INNER JOIN tblcrew ON `tblcrew`.`crewId`=`tblScan`.`crewId`
GROUP BY `tblScan`.`crewId`
Optimizing mysql subquery for multiple INs

Optimizing mysql subquery for multiple INs

By : Tainá Zaqui
Date : March 29 2020, 07:55 AM
should help you out First, you should have indexes for article in table products and for item in table structure.
If you always have at least one row in structure for a given product, you could give this a try:
code :
SELECT s.final_item, p.article
    FROM  `structure` s INNER JOIN products p ON s.item = p.article
    WHERE s.article IN ('200101','200102')
    ORDER BY s.level DESC 
    LIMIT 1
MySQL Optimizing a subquery which uses a WHERE clause?

MySQL Optimizing a subquery which uses a WHERE clause?

By : user2772383
Date : March 29 2020, 07:55 AM
this will help Sub queries are often not great in MySQL due to not using indexes for the joins.
However it might be worth trying a sub query with a join, rather than a sub query with a sub query:-
code :
LEFT JOIN (SELECT s1.product_id, MAX(s1.offer_date) AS sec_last_date 
           FROM t_offers AS s1  
           INNER JOIN t_offers AS s2
           ON s2.product_id = s1.product_id
           AND s2.offer_date > s1.offer_date
           GROUP BY s1.product_id) AS t2 ON t2.product_id=p.id 
Related Posts Related Posts :
  • select the records with the highest amount
  • Changing Mysql golbal variable
  • How to create Effective Indexing on MySQL
  • `require': Incorrect MySQL client library version
  • How to save a FirstName of a Person efficiently without duplicate entries
  • Can I store my own sql query by mysql special function and execute stored query later?
  • MySQL comma separated field query
  • Why does the same exact query produce 2 different MySQL explain results?
  • Suppress warning output in bash
  • Doctrine "on update CURRENT_TIMESTAMP" annotation (Symfony2)
  • Designing "Friend" relationships across two mysql tables
  • Importing sql file using phpmyadmin in EasyPHP
  • Easy PHP and mysql ..php cannot see database on local pc (all works on server)
  • MySQL join optimization - bypassing filesort
  • How to Select record with the maximum value in a GROUP BY?
  • MySQL Innodb Full text Proximity Search Gives Horrible Performance
  • MySQL best approach for db normalising, relationships and foreign keys
  • How to update one table based on the count value of another table while matching ids?
  • MAMP Pro 5.1.1-terminates MySQL when quitting
  • SQL - Get date of most votes cast
  • "Fuzzier" search in mysql
  • Tracing mysqld Using SystemTap
  • SELECT + INSERT + Query Cache = MySQL lock up
  • SQL vs. NoSQL for medium complexity search systems
  • SQL Error when creating table
  • Is it possible to write a query to compare rows to other rows in same table?
  • Display all duplicate records based multiple columns
  • summing time column in mysql
  • InnoDB: Cannot open table
  • Why is IN() considered O(logN) operation?
  • Can a deadlock occur on commit?
  • Is there a fast way to do a '%phrase%' search in any DB?
  • Is using an IN over a huge data set a good idea?
  • How can I know if a table is already arranged in ascending order in MySQL?
  • MySQL - Designing database for a simple game
  • Why am I getting "Host '' is not allowed to connect to this MySQL server"?
  • what type of password hash? possible mysql hash?
  • MySQL - Using a date range vs functions
  • Using IS NULL and COALESCE in OrderBy Doctrine Querybuilder
  • How to merge MySQL columns into one column if there are empty values in the table?
  • Cardinality Confusion
  • Renaming column multiple ids in SELECT
  • Group all from and to messages per user
  • How to handled the null values in WHERE IN condition in mysql
  • Is it okay to update primary key field to shift a record to the top?
  • Stop query through pdo
  • How to check whether particular value in field in MySQL exists
  • Execute a statement for every table in a database
  • insertion 74G data into mysql table cost more then 2 days, how to improve insert performance
  • Where can I see the differents "Hibernate Console Configurations" in Eclipse
  • MySql | relational database vs non relational database in terms of Performance
  • Exporting mysql database using mysqldump including procedures
  • Trigger MySQL not working
  • How do I update values for individual rows quickly?
  • MySQL join query with multiple where condition
  • MySQL stored procedure is not working
  • MySQL - Order By exact match at the end
  • Select max date or null date from same table MySQL
  • Best solution workaround for needing a mysql event on insert?
  • MySQL select several columns of several tables at the same time without using JOIN
  • shadow
    Privacy Policy - Terms - Contact Us © ourworld-yourmove.org