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JOINS
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JOINS Joins are used data from 2 or more tables , which is joined to appear as single set of data. Used for combining columns from two or more tables by using values – common to both tables. Join keyword is used in SQL Queries for joining two or more tables. Minimum required condition for joining table , is (n-1) where ‘n’ – no. of tables. Tuesday, July 21, 2015
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Types Equi join Non - Equi join Self join Natural join Cross join
Outer join Left outer Right outer Full outer Inner join Tuesday, July 21, 2015
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SQL> select * from emp_dept;
Table 1 : emp_dept SQL> select * from emp_dept; DEPTNO DNAME LOC 10 INVENTORY HYBD 20 FINANCE B’LORE 30 HR MUMBAI Table 2 : emprefer SQL> select * from emprefer; EMPNO ENAME JOB MGR DEPTNO 111 Saketh Analyst 444 10 222 Sudha Clerk 333 20 Jagan Manager Madhu Engineer T4u0esday, July 21, 2015
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INNER JOIN BTGuLesRday,
This will display all the records that have matched. Ex: SQL> select empno , ename , job , dname , loc from emprefer inner join emp_dept using(deptno); EMPNO ENAME JOB DNAME LOC 111 saketh analyst Inventory HYBD 333 jagan manager 222 sudha clerkx` Finance BTGuLesRday, July 21, 2015
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OUTER JOIN Outer join gives the non-matching records along with matching records. Types of Outer Join Left Outer Join ( Matching Rows + Non - matching rows from left table) Right Outer Join ( Matching Rows + Non - matching rows from right table) Full Outer Join ( Matching Rows + Non - matching rows from both the table) Tuesday, July 21, 2015
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LEFT OUTER JOIN This will display the all matching records and the records which are in left hand side table those that are not in right hand side table. SQL> select empno , ename , job , dname , loc from emprefer e left outer join emp_dept d on(e.deptno=d.deptno); Or SQL> select empno , ename , job , dname , loc from emprefer e , emp_dept d where e.deptno = d.deptno(+); EMPNO ENAME JOB DNAME LOC 111 Saketh Analyst inventory HYBD 333 Jagan Manager 222 Sudha Clerk finance BGLR 444 Madhu Engineer Tuesday, July 21, 2015
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RIGHT OUTER JOIN This will display the all matching records and the records which are in right hand side table those that are not in left hand side table. Ex: SQL> select empno , ename , job , dname , loc from emprefer e right outer join dept d on(e.deptno=d.deptno); Or SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno(+) = d.deptno; EMPNO ENAME JOB DNAME LOC 111 Saketh Analyst INVENTORY HYBD 333 Jagan Manager 222 Sudha Clerk FINANCE BGLR HR MUMBAI Tuesday, July 21, 2015
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FULL OUTER JOIN This will display the all matching records and the non-matching records from both tables. Ex: SQL> select empno , ename , job , dname , loc from emprefer e full outer join emp_dept d on(e.deptno = d.deptno); EMPNO ENAME JOB DNAME LOC 333 jagan manager INVENTORY HYBD 111 saketh analyst 222 sudha clerk FINANCE BGLR 444 madhu engineer HR MUMBAI Tuesday, July 21, 2015
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EQUI JOIN A join which contains an equal to ‘=’ operator in the joins condition. Ex: SQL> select empno , ename , job , dname , loc from emprefer e , emp_dept d where e.deptno = d.deptno; EMPNO ENAME JOB DNAME LOC 111 Saketh Analyst inventory HYBD 333 Jagan Manager 222 Sudha Clerk finance BGLR Tuesday, July 21, 2015
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NON-EQUI JOIN A join which contains an operator other than equal to ‘=’ in the joins condition. Ex: SQL> select empno , ename , job , dname , loc from emprefer e , emp_dept d where e.deptno > d.deptno; EMPNO ENAME JOB DNAME LOC 222 sudha clerk INVENTORY HYBD 444 madhu engineer FINANCE BGLR HR MUMBAI Tuesday, July 21, 2015
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SELF JOIN Joining the table itself is called self join. Ex:
SQL> select e1.empno , e2.ename , e1.job , e2.deptno from emprefer e1 , emprefer e2 where e1.empno = e2.mgr; EMPNO ENAME JOB DEPTNO 111 jagan analyst 10 222 madhu clerk 40 333 sudha manager 20 444 saketh engineer Tuesday, July 21, 2015
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NATURAL JOIN Natural join compares all the common columns. Ex:
SQL> select empno , ename , job , dname , loc from emprefer natural join emp_dept; EMPNO ENAME JOB DNAME 111 saketh analyst Inventory 333 jagan manager 222 sudha clerk Finance Tuesday, July 21, 2015
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CROSS JOIN This will gives the cross product. Ex:
SQL> select empno , ename , job , dname , loc from emprefer cross join emp_dept; EMPNO ENAME JOB DNAME LOC 111 saketh analyst INVENTORY HYBD 222 sudha clerk 333 jagan manager 444 madhu engineer FINANCE BGLR HR MUMBAI Tuesday, July 21, 2015
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THANK YOU ... Tuesday, July 21, 2015
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