1. Three-table joint query select Xx,xx from a, B, C Cartesian product, equivalent to cross join 4. Cross join--lists all combinations on both sides, also called Descartes set A.rows * b.rowsselect *from Sales S Cross join Customers C 5. INNER JOIN = join--Both sides are filtered out select *from Sales S inner JOIN Customers Con s.cust_id = c.cust_id 2. Left join = outer join--with the table on the main table, lists all records of the primary table, matches the match, matches with null list select * FROM Customers C left join sales son c.cust_id = S.CUST_ID 3. Right join = Outer join--takes the table on the left as the main table, lists all records of the primary table, matches the match, matches the mismatch with null, lists the SELECT * from the Customers C right join sales son c.cust_i D = s.cust_id 6. Full join = Full outer join--are listed on both sides, matching on match, mismatched with null list select *from Sales S full outer join Customers Con s.cust_id = C.cus t_idExample ======================SELECT a.id, rule_id, Alarm_name, Filter_key, A.subtype, B.name
From (A
Left JOIN B on a.subtype = b.id)
JOIN C on c.alarm_type = A.type
"MySQL" Federated query
