SELECT * FROM prod_2_cat p2c INNER JOIN product_yahoo p ON p.id =  p2c.id INNER JOIN categories c ON p2c.cats = c.id WHERE p2c.cats = 4


// EXPLAIN


id 	select_type 	table 	type 	possible_keys 	key 	key_len 	ref 	rows 	Extra
1 	SIMPLE 	p2c 	system 	id,cats 	NULL 	NULL 	NULL 	1 	 
1 	SIMPLE 	c 	const 	PRIMARY 	PRIMARY 	4 	const 	1 	 
1 	SIMPLE 	p 	ref 	id 	id 	102 	const 	1 	Using where