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Tell me in non-technical terms the difference between an

  inner join & outter join? (SQL)

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Diff btwn inner and outer join: Inner joins/Equi/Simple are both same and purpose in to fetch common rows from 2 or more joining tables. condition to satify would be each table shud and must have common col to perform inner join. simple syntax would be : select t1.col1,t1.col2,t2.col1 from t1,t2 where t1.col=t2.col On other hand Outer join fetches all col from both tables.regardless both tables have matching col or not Outer join is further divided in to left,right,full Outer Joins. Left Outer join:ex T1-employee,T2-dept This join is used to fetch all col of T1 example for this is to find the employees who are not assigned to any departments select e.ename,d.dname from employee e depatment d where e.d_id = d.d_id(+) OR select e.ename,d.dname LEFT outer join dept on e.d_id = d.d_id Right Outer Join each row of t2 will appear at-least once non matching row of table in displayed with NULL use of this query is to find out dept which has no employees assigned and also to get details of each emp assigned to which dept . select e.ename,d.dname from employee e depatment d where e.d_id(+) = d.d_id OR select e.ename,d.dname RIGHT outer join dept on e.d_id = d.d_id FULL Outer join: combines both effect of right and left outer joins Allows to see each emp who is in which dept and also each emp who is not part of any dept and each dept which doesnt have emp

Anonymous on Jun 8, 2015

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