My Experience Joins And Its Types.

krishatg

Yellow Belt
Joins are basically used to combile two or more tables i.e in order to retrieve the data stored in 2 different table we need to join those tables in a query.
There are various types of joins:
  • Theta or Equi join: In this condition to join 2 or more tables are specified by = operator. Eg: Select e.name,e.product, c.customer from emp_prod e, prod_cust c where e.product=c.product.
  • Non-equi join: In this condition to join 2 or more tables are specified by operators other than =. Eg: Select e.name,d.deptno from emp e, dept d where e.sal between d.lowsal and d.hisal;
  • Outer join: when we want to include the row of the table even there is no corresponding row in another table.There are 2 types of outer joins: 1.Right outer join and 2. Left outer join.
  • Self Join: self joins are used when we want to join a table to itself.EG: Select e.name, e.product from emp_prod e, emp_prod m where e.prodid = m.prodid;
 

Swati Mishra

Yellow Belt
Each join have their own property. these are the also more joins such as the
natural join,
cross join,
outer join
inner join
 
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