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Using GROUP BY and MAX on multiple columns in MySQL?
To understand the GROUP BY and MAX on multiple columns, let us first create a table. The query to create a table is as follows −
mysql> create table GroupByMaxDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> CategoryId int, -> Value1 int, -> Value2 int -> ); Query OK, 0 rows affected (0.68 sec)
Example
Insert some records in the table using insert command. The query is as follows −
mysql> insert into GroupByMaxDemo(CategoryId, Value1,Value2) values(10,100,50); Query OK, 1 row affected (0.15 sec) mysql> insert into GroupByMaxDemo(CategoryId, Value1,Value2) values(10,100,70); Query OK, 1 row affected (0.21 sec) mysql> insert into GroupByMaxDemo(CategoryId, Value1,Value2) values(10,50,100); Query OK, 1 row affected (0.22 sec) mysql> insert into GroupByMaxDemo(CategoryId, Value1,Value2) values(20,180,150); Query OK, 1 row affected (0.19 sec)
Display all records from the table using a select statement. The query is as follows −
mysql> select *from GroupByMaxDemo;
Output
+----+------------+--------+--------+ | Id | CategoryId | Value1 | Value2 | +----+------------+--------+--------+ | 1 | 10 | 100 | 50 | | 2 | 10 | 100 | 70 | | 3 | 10 | 50 | 100 | | 4 | 20 | 180 | 150 | +----+------------+--------+--------+ 4 rows in set (0.00 sec)
Example
The following is the query to use GROUP BY and MAX on multiple columns −
mysql> select tbl2.CategoryId, tbl2.Value1, max(tbl2.Value2) -> from -> ( -> select CategoryId, max(Value1) as `Value1` -> from GroupByMaxDemo -> group by CategoryId -> ) tbl1 -> inner join GroupByMaxDemo tbl2 on tbl2.CategoryId = tbl1.CategoryId and tbl2.Value1 = tbl1.Value1 -> group by tbl2.CategoryId, tbl2.Value1;
Output
+------------+--------+------------------+ | CategoryId | Value1 | max(tbl2.Value2) | +------------+--------+------------------+ | 10 | 100 | 70 | | 20 | 180 | 150 | +------------+--------+------------------+ 2 rows in set (0.00 sec)
Updated on: 26-Jun-2020
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