MySQL COUNT() function with group by

COUNT() function with group by

In this page we have discussed how to use MySQL COUNT() function with GROUP BY.

Example:

The following MySQL statement will show number of author for each country. The GROUP BY clause groups all records for each country and then COUNT() function in conjunction with GROUP BY counts the number of authors for each country.

Sample table: author

Code:

SELECT country,COUNT(*)
FROM author      
GROUP BY country;

Output:

mysql> SELECT country, COUNT(*)
    -> FROM author
    -> GROUP BY country;
+-----------+----------+
| country   | COUNT(*) |
+-----------+----------+
| Australia |        2 | 
| Brazil    |        1 | 
| Canada    |        2 | 
| Germany   |        1 | 
| India     |        1 | 
| UK        |        4 | 
| USA       |        4 | 
+-----------+----------+
7 rows in set (0.00 sec)

Pictorial Presentation:

MySQL COUNT() function with group by on multiple columns

The following MySQL statement returns number of publishers in each city for a country. Grouping operation is performed on country and pub_city column with the use of GROUP BY and then COUNT() counts the number of publishers for each groups.

Sample table: publisher

Code:

SELECT country,pub_city,COUNT(*)
FROM publisher  
GROUP BY country,pub_city; 

Output:

mysql> SELECT country,pub_city,COUNT(*)
    -> FROM publisher
    -> GROUP BY country,pub_city;
+-----------+-----------+----------+
| country   | pub_city  | COUNT(*) |
+-----------+-----------+----------+
| Australia | Adelaide  |        1 | 
| India     | Mumbai    |        1 | 
| India     | New Delhi |        1 | 
| UK        | Cambridge |        1 | 
| UK        | London    |        1 | 
| USA       | Houstan   |        1 | 
| USA       | New York  |        2 | 
+-----------+-----------+----------+
7 rows in set (0.00 sec)

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