Shulou(Shulou.com)06/01 Report--

1. Cartesian product select * from emp,dep; select * from emp,dep where emp.dep_id = dep.id;select * from emp,dep where emp.dep_id = dep.id and dep.name = "technology"; 2. Inner join: only take records select * from emp inner join dep on emp.dep_id = dep.id that have corresponding relations between two tables Select * from emp inner join dep on emp.dep_id = dep.id where dep.name = "technology"; inner join join two tables, where filter condition, only take the conditions meet 3. Left join: keep the record select * from emp left join dep on emp.dep_id = dep.id without corresponding relationship in the left table on the basis of inner join 4. Right join: keep records with no corresponding relationship in the right table select * from emp right join dep on emp.dep_id = dep.id;5, full join: keep records with no corresponding relationship in the left and right tables on the basis of internal connection: select * from emp left join dep on emp.dep_id = dep.idunionselect * from emp right join dep on emp.dep_id = dep.id

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