{"id":30451,"date":"2019-04-10T17:17:46","date_gmt":"2019-04-10T08:17:46","guid":{"rendered":"https:\/\/jirak.net\/wp\/removal-of-implicit-and-explicit-sorting-for-group-by\/"},"modified":"2019-04-10T17:34:27","modified_gmt":"2019-04-10T08:34:27","slug":"removal-of-implicit-and-explicit-sorting-for-group-by","status":"publish","type":"post","link":"https:\/\/jirak.net\/wp\/removal-of-implicit-and-explicit-sorting-for-group-by\/","title":{"rendered":"Removal of implicit and explicit sorting for GROUP BY"},"content":{"rendered":"

Removal of implicit and explicit sorting for GROUP BY<\/p>\n

In MySQL, historically GROUP BY was used to provide sorting as well. If a query specified GROUP BY, the result was sorted as if ORDER BY was present in the query.<\/p>\n

mysql-5.7> CREATE TABLE t (id INTEGER,  cnt INTEGER);\r\nQuery OK, 0 rows affected (0.03 sec)\r\n\r\nmysql-5.7> INSERT INTO t VALUES (4,1),(3,2),(1,4),(2,2),(1,1),(1,5),(2,6),(2,1),(1,3),(3,4),(4,5),(3,6);\r\nQuery OK, 12 rows affected (0.02 sec)\r\nRecords: 12  Duplicates: 0  Warnings: 0\r\n\r\nmysql-5.7> SELECT id, SUM(cnt) FROM t GROUP BY id;\r\n+------+----------+\r\n| id   | SUM(cnt) |\r\n+------+----------+\r\n|    1 |       13 |\r\n|    2 |        9 |\r\n|    3 |       12 |\r\n|    4 |        6 |\r\n+------+----------+\r\n4 rows in set (0.00 sec)<\/pre>\n
MySQL here implicitly sorts the results from GROUP BY (i.e.…<\/p>\n
\n