join sql command code example

Example 1: join three tables sql

Suppose we are having three table named as 
Student_details
Attendance_details
Batch_details
And we have to apply join these three tables for fetching records

Example query:
select column_names
from Student_detail as s join Attendance_details as a on
s.s_id = a.s_id join Batch_details as b on 
s.s_id = b.s_id;

Here in the above example we implemented simple join but you change it with own join requirements.

Example 2: joins in sql

INNER JOIN:
is used when retrieving data from multiple
tables and will return only matching data.

LEFT OUTER JOIN:
is used when retrieving data from
multiple tables and will return
left table and any matching right table records.

RIGHT OUTER JOIN:
is used when retrieving data from
multiple tables and will return right
table and any matching left table records

FULL OUTER JOIN:
is used when retrieving data from
multiple tables and will return both
table records, matching and non-matching.



INNER JOIN :
SELECT select_list From TableA A
Inner Join TableB B
On A.Key = B.Key


LEFT OUTER JOIN :
SELECT select_list From TableA A
Left Join TableB B
On A.Key = B.Key

(where b.key is null)//For delete matching data



RIGTH OUTER JOIN :
SELECT select_list From TableA A
Right Join TableB B
On A.Key = B.Key


FULL JOIN :
SELECT select_list From TableA A
FULL OUTER Join TableB B
On A.Key = B.Key