SQL Group By
The SQL GROUP BY is used when at least one of the aggregation functions is used in a select query.
The aggregate functions are: count, max, min, sum, avg.
Group By syntax
SELECT column_name1, column_name2, function(column_name1)
FROM table_name
GROUP BY column_name1, column_name2
Group By example
Coder books table
| ID |
Title |
Price |
Description |
| 1 |
Learn SQL |
20 |
Learn SQL language |
| 2 |
Learn MySQL |
22 |
Learn MySQL language |
| 3 |
HTML book |
17 |
Learn HTML |
| 4 |
Learn PHP |
20 |
Introduction to PHP |
| 5 |
Learn PHP |
20 |
PHP course |
SELECT id, title, price, count(price) p_count
FROM coder_books
GROUP BY id, title, price
Result
| ID |
Title |
Price |
p_count |
| 1 |
Learn SQL |
20 |
1 |
| 2 |
Learn MySQL |
22 |
1 |
| 3 |
HTML book |
17 |
1 |
| 4 |
Learn PHP |
20 |
1 |
| 5 |
Learn PHP |
20 |
1 |
SELECT price, count(price) p_count
FROM coder_books
GROUP BY price
HAVING count(*) > 0
Result
| Price |
p_count |
| 17 |
1 |
| 20 |
3 |
| 22 |
1 |