If we need to group rows with the same values into summary rows, we use GROUP BY.
GROUP BY is often used with aggregation functions (SUM, MIN, MAX, AVG, COUNT).
Structure:
SELECT column_name
FROM table_name
WHERE condition
GROUP BY column_name
ORDER BY column_name;
Example1:
We have a table Customer with this data:
CustomerID Name Hair Salary 1 Alechandro brown 100 2 Katerina blonde 150 3 Lucie blonde 30 4 Thomas black 40 5 Theodor black 120 6 Thomassino black 99 7 Knor brown 50 8 Thor blonde 10 9 Lucie pink 70
SELECT name, COUNT(salary)
FROM Customer
GROUP BY name;
The result will be this:
NAME COUNT(SALARY) Thomas 1 Knor 1 Katerina 1 Thor 1 Lucie 2 Thomassino 1 Alechandro 1 Theodor 1
Example2:
We have a table Customer with this data:
CustomerID Name Hair Salary 1 Alechandro brown 100 2 Katerina blonde 150 3 Lucie blonde 30 4 Thomas black 40 5 Theodor black 120 6 Thomassino black 99 7 Knor brown 50 8 Thor blonde 10 9 Lucie pink 70
SELECT name, COUNT(salary)
FROM Customer
GROUP BY name
ORDER BY name;
The result will be this:
NAME COUNT(SALARY) Alechandro 1 Katerina 1 Knor 1 Lucie 2 Theodor 1 Thomas 1 Thomassino 1 Thor 1
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