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What's a reasonable number of rows and tables to be able to join in MySQL?


What's a reasonable number of rows and tables to be able to join in MySQL?

By : Scotty
Date : November 20 2020, 07:00 PM
With these it helps MySQL is perfectly capable of handling joins involving 5 million rows or even many more than this.
Your problem is probably one of two things:
code :


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How can I join two tables with different number of rows in MySQL?

How can I join two tables with different number of rows in MySQL?


By : Kine C.
Date : March 29 2020, 07:55 AM
I wish did fix the issue. If you want all the results, you need an outer join, not an inner one. (Inner only returns the rows where there is a match; outer returns all rows, with the matching rows "stitched together")
MySQL JOIN two tables with different number of rows by id

MySQL JOIN two tables with different number of rows by id


By : Lawrence Neibauer
Date : March 29 2020, 07:55 AM
wish of those help I have two tables. , This should work fine:
code :
SELECT 
  t2.id     AS column1,
  t1.column AS column2
FROM table2 AS t2
LEFT JOIN table1 AS t1 ON t1.id = t2.column;
| COLUMN1 | COLUMN2 |
---------------------
|      10 |      23 |
|      11 |      23 |
|      21 |      34 |
|      33 |      99 |
LIMIT number of rows in a JOIN between MySQL tables

LIMIT number of rows in a JOIN between MySQL tables


By : user1490056
Date : March 29 2020, 07:55 AM
around this issue A combination of 'group_concat' and 'find_in_set', followed by the filtering using the position returned by 'find_in_set' will do the job for you.
GROUP_CONCAT will sort the data in descending order of points first.
code :
GROUP_CONCAT(Run ORDER BY Points DESC)
FIND_IN_SET(Run, grouped_run) BETWEEN 1 AND Users.NumberOfRun
SELECT
  Runs.*
FROM
  Runs 
  INNER JOIN (
    SELECT
      Name, GROUP_CONCAT(Run ORDER BY Points DESC) grouped_run
    FROM
      Runs
    GROUP BY Name
  ) group_max ON Runs.Name = group_max.Name
  INNER JOIN Users ON Users.Name = Runs.Name
  WHERE FIND_IN_SET(Run, grouped_run) BETWEEN 1 AND Users.NumberOfRun
ORDER BY
  Runs.Name Asc, Runs.Points DESC;
How to count number of rows in other tables using mysql inner join?

How to count number of rows in other tables using mysql inner join?


By : lucas
Date : March 29 2020, 07:55 AM
wish of those help Try below query: you need to count progress_id and notification_id which are associated with certain customer
code :
SELECT `cc`.`customer_id`, `cc`.`customer_name`, COUNT(distinct `cp`.`progress_id`) AS Progress, COUNT(distinct `cn`.`notification_id`) AS Notifications 
FROM `crm_customers` AS `cc` INNER JOIN `crm_progress` AS `cp` 
ON `cc`.`customer_id` = `cp`.`progress_customer` 
INNER JOIN `crm_notifications` AS `cn` 
ON `cn`.`notification_customer` = `cp`.`progress_customer` 
WHERE `cc`.`customer_id` = 1 AND `cc`.`customer_status` = 1 
group by `cc`.`customer_id`, `cc`.`customer_name`
MySQL Whats better for speed one table with millions of rows or managing multiple tables?

MySQL Whats better for speed one table with millions of rows or managing multiple tables?


By : Denis Rodriguez
Date : March 29 2020, 07:55 AM
it helps some times Given 105 rows and 102 CSVs per day, you're looking at 10 million rows per day (and you say you'll clear that data down regularly). That doesn't look like a scary figure for a decent db (especially given that you can index within tables, and not across multiple tables).
Obviously the most regularly used CSVs could be very easily held in memory for speed of access - perhaps even all of them (a very simple calculation based on next to no data gives me a figure of 1Gb if you flush every over 24 hours. 1Gb is not an unreasonable amount of memory these days)
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