mysql复杂选择，左联接

Question

I have 3 tables, a,b,c

It is possible to add left join for two table select add 3rd table by left join:

example:

SELECT * from a,b where  a.x=b.x and a.z=b.z and b.y>0 

(there I need select only that records where I can found exact matches by that rules)

now I want add some fields from 3rd table, but there are possible situation that 3rd table may not contain data for some table a,b records. As I understand I can use left join ?

I How can select something this:

SELECT a.*,b.*, c.Q from a,b where  a.x=b.x and a.z=b.z and b.y>0  left join c on a.x=c.x 

Answer 1

If you don't like writing INNER JOINs:

SELECT a.*,b.*, c.Q 
FROM (a,b)  
LEFT JOIN c 
ON a.x=c.x 
WHERE a.x=b.x and a.z=b.z and b.y>0

Answer 2

SELECT a.*,b.*, c.Q 
FROM a 
INNER JOIN b 
  ON a.x=b.x AND a.z=b.z AND b.y>0
LEFT JOIN c 
  ON a.x=c.x