Joins in database, We can easily determine the meaning of joins very easily. In database we use the concept of joining in tables to fetch the data combination. There
are different type of methods of joining two or more than two tables in database. You can categories joins in two simple types. one is inner join and outer join.
We are here to discuss the outer joins only. Lets discuss the outer joins.
Outer joins are useful to get the records if it does not match with other table records. It means joined table will retains all the records if matching records not
available. Lets take an small example. Suppose we have two table one is emp and other is salary.
Emp
Id |
Name |
1 |
Tom |
2 |
Sommy |
3 |
Bunny |
4 |
Runny |
Salary
Id |
salary |
1 |
1004 |
4 |
2443 |
3 |
342323 |
5 |
2423 |
You can create mysql query for joining these two tables with outer join.
SELECT * from emp as e LEFT OUTER JOIN salary as s on s.Id=e.Id
e.Id |
e.Name |
s.Id |
s.salary |
1 |
Tom |
1 |
1004 |
2 |
Sommy |
2 |
NULL |
3 |
Bunny |
3 |
342323 |
4 |
Runny |
4 |
2443 |
NULL |
NULL |
5 |
2423 |
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