Question

I have two tables. The name table have a foreign key named ‘categories’. The other table is ‘categories’ that contains name of the categories. The name table references a category in the categories table.

So I use this:

$categories = "SELECT name, COUNT(*) category";
$number_of_categories = "SELECT category, COUNT(1) FROM name GROUP BY category";

As you can see, I’m doing two select statements. I heard that joining tables can do magic, please teach me how to do this in one SELECT statement.

Basically I want to SELECT all the rows from the category table, and then count the number of instances of each category in the name table.

Answer 1

SELECT c.name, COUNT(n.category) AS count_in_name_table
FROM categories c
LEFT JOIN name n ON n.category = c.name
GROUP BY c.name