Simple way to calculate median with MySQL

In MariaDB / MySQL:

SELECT AVG(dd.val) as median_val
FROM (
SELECT d.val, @rownum:=@rownum+1 as `row_number`, @total_rows:=@rownum
  FROM data d, (SELECT @rownum:=0) r
  WHERE d.val is NOT NULL
  -- put some where clause here
  ORDER BY d.val
) as dd
WHERE dd.row_number IN ( FLOOR((@total_rows+1)/2), FLOOR((@total_rows+2)/2) );

Steve Cohen points out, that after the first pass, @rownum will contain the total number of rows. This can be used to determine the median, so no second pass or join is needed.

Also AVG(dd.val) and dd.row_number IN(...) is used to correctly produce a median when there are an even number of records. Reasoning:

SELECT FLOOR((3+1)/2),FLOOR((3+2)/2); -- when total_rows is 3, avg rows 2 and 2
SELECT FLOOR((4+1)/2),FLOOR((4+2)/2); -- when total_rows is 4, avg rows 2 and 3

Finally, MariaDB 10.3.3+ contains a MEDIAN function

Related Posts:

  1. MySQL Error: : ‘Access denied for user ‘root’@’localhost’
  2. Unknown column in ‘field list’ error on MySQL Update query
  3. Unknown column in ‘field list’ error on MySQL Update query
  4. MySQL – Operand should contain 1 column(s)
  5. MySQL “CREATE TABLE IF NOT EXISTS” -> Error 1050
  6. MySQL Error: : ‘Access denied for user ‘root’@’localhost’
  7. MySQL create table if not exists and insert record only if table was created
  8. How do I use properly CASE..WHEN in MySQL
  9. How can I do a FULL OUTER JOIN in MySQL?
  10. MySQL query String contains
  11. What’s the difference between VARCHAR and CHAR?
  12. Case statement in MySQL
  13. How to declare a variable in MySQL?
  14. MySQL Cannot Add Foreign Key Constraint
  15. How to split the name string in mysql?
  16. How do I import an SQL file using the command line in MySQL?
  17. Can’t connect to local MySQL server through socket ‘/tmp/mysql.sock’ (2)
  18. mysql Foreign key constraint is incorrectly formed error
  19. MySQL: Invalid use of group function
  20. How can I return pivot table output in MySQL?
  21. Compare dates in MySQL
  22. MySQL “WITH” clause
  23. MySQL Multiple Joins in one query?
  24. Error Code: 2013. Lost connection to MySQL server during query
  25. MySQL syntax for Join Update
  26. Can’t connect to local MySQL server through socket ‘/tmp/mysql.sock’ (2)
  27. how to drop partition without dropping data in MySQL?
  28. MySQL combine two columns into one column
  29. Error 1046 No database Selected, how to resolve?
  30. MySQL Error 1264: out of range value for column
  31. Remove duplicate rows in MySQL
  32. How to SUM and SUBTRACT using SQL?
  33. Cast from VARCHAR to INT – MySQL
  34. SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax — PHP — PDO [duplicate]
  35. How do you force mysql LIKE to be case sensitive?
  36. MySQL – UPDATE multiple rows with different values in one query
  37. How to create a MySQL hierarchical recursive query?
  38. ERROR 1148: The used command is not allowed with this MySQL version
  39. Insert into a MySQL table or update if exists
  40. How to round down to nearest integer in MySQL?
  41. MySQL starts with searching issue
  42. Query to convert from datetime to date mysql
  43. Is it possible to GROUP BY multiple columns using MySQL?
  44. MySQL error: key specification without a key length
  45. Best way to test if a row exists in a MySQL table
  46. Check if MySQL table exists without using “select from” syntax?
  47. MySQL equivalent of DECODE function in Oracle
  48. mysql update column with value from another table
  49. The used SELECT statements have a different number of columns
  50. How to delete from multiple tables in MySQL?
  51. MySQL: Can’t create table (errno: 150)
  52. How to copy a row and insert in same table with a autoincrement field in MySQL?
  53. Join vs. sub-query
  54. Alternative to except in MySQL
  55. Equivalent of explode() to work with strings in MySQL
  56. ROW_NUMBER() in MySQ
  57. MySQL OPTIMIZE all tables?
  58. MySQL INSERT INTO table VALUES.. vs INSERT INTO table SET
  59. MySQL – Get row number on select
  60. MySQL error: Unknown column in ‘where clause’
  61. How to truncate the text returned for a column in a MySQL query
  62. Using union and order by clause in mysql
  63. MySQL LIKE IN()?
  64. Conversion failed when converting date and/or time from character string while inserting datetime
  65. error, string or binary data would be truncated when trying to insert
  66. Using group by on multiple columns
  67. ORA-01843 not a valid month- Comparing Dates
  68. How do I escape a single quote in SQL Server?
  69. Creating a search form in PHP to search a database?
  70. The ALTER TABLE statement conflicted with the FOREIGN KEY constraint
  71. Simple Random Samples from a Sql database
  72. What does SQL clause “GROUP BY 1” mean?
  73. SELECT DISTINCT on one column
  74. SQL select only rows with max value on a column
  75. TSQL PIVOT MULTIPLE COLUMNS
  76. Microsoft OLE DB Provider for SQL Server error ‘80004005’
  77. Equivalent of Oracle’s RowID in SQL Server
  78. Subtract one day from datetime
  79. Backup a single table with its data from a database in sql server 2008
  80. updating table rows in postgres using subquery
  81. Is there a coalesce-like function in Excel?
  82. PHP Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in /home/website/public_html/facebook/fbclogin.php on line 57 [duplicate]
  83. ora-06553 pls-306 wrong number or types of arguments in call to ‘ogc_x’
  84. SQL query to extract only the “current” wp_posts?
  85. How to retrieve sticky post in raw sql?
  86. Would manually deleting the dumping data fix a “#1062 – Duplicate entry ‘1’ for key ‘PRIMARY'” phpMyAdmin error?
  87. Backticks (`) Instead of Single Quotes (‘) in an SQL Statement?
  88. SQL User Query by Multiple Roles using PHP
  89. $wpdb get_var issue
  90. Inserting rows into a custom table, when plugin is activated
  91. Posts modified in the last 48 hours
  92. post id not displaying
  93. How to run complex query using PHP
  94. Bulk find & replace on WordPress posts/pages (minus image paths)
  95. Improving performance of SQL sub-queries in WordPress
  96. Insert multiple checkbox values
  97. How to get EVENT based on startday, using BETWEEN
  98. SQL Query to get post_id from wp_posts and and meta_key(s) from wp_postmeta
  99. SQL get last entry of a specific gravity form
  100. Deleting the MySQL database

Leave a Comment