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> create table emp(empid INT, name text, dept_id int, salary int);
> Insert into emp values(1,'Rob', 1, 100);
> Insert into emp values(2,'Mark', 1, 300);
> Insert into emp values(3,'John', 2, 100);
> Insert into emp values(4,'Mary', 2, 300);
> Insert into emp values(5,'Bill', 3, 700);
> Insert into emp values(6,'Jose', 6, 400);
>
>
> create table department(deptid INT, name text);
> Insert into department values(1,'IT');
> Insert into department values(2,'Accounts');
> Insert into department values(3,'Security');
> Insert into department values(4,'HR');
> Insert into department values(5,'R&D');
>
>
> <pre>
> ✓
>
1 rows affected
>
1 rows affected
>
1 rows affected
>
1 rows affected
>
1 rows affected
>
1 rows affected
>
> ✓
>
1 rows affected
>
1 rows affected
>
1 rows affected
>
1 rows affected
>
1 rows affected
> </pre>
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> Select * from emp;
>
>
> <pre>
> empid | name | dept_id | salary
> ----: | :--- | ------: | -----:
> 1 | Rob | 1 | 100
> 2 | Mark | 1 | 300
> 3 | John | 2 | 100
> 4 | Mary | 2 | 300
> 5 | Bill | 3 | 700
> 6 | Jose | 6 | 400
> </pre>
<!-- -->
> Select * from department;
>
> <pre>
> deptid | name
> -----: | :-------
> 1 | IT
> 2 | Accounts
> 3 | Security
> 4 | HR
> 5 | R&D
> </pre>
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> -- INNER JOIN
>
> Select a.empid, a.name, b.name as dept_name
> FROM emp a
> JOIN department b
> ON a.dept_id = b.deptid
> ;
>
> <pre>
> empid | name | dept_name
> ----: | :--- | :--------
> 1 | Rob | IT
> 2 | Mark | IT
> 3 | John | Accounts
> 4 | Mary | Accounts
> 5 | Bill | Security
> </pre>
<!-- -->
> -- LEFT JOIN
>
> Select a.empid, a.name, b.name as dept_name
> FROM emp a
> LEFT JOIN department b
> ON a.dept_id = b.deptid
> ;
>
> <pre>
> empid | name | dept_name
> ----: | :--- | :--------
> 1 | Rob | IT
> 2 | Mark | IT
> 3 | John | Accounts
> 4 | Mary | Accounts
> 5 | Bill | Security
> 6 | Jose | <em>null</em>
> </pre>
*db<>fiddle [here](https://dbfiddle.uk/?rdbms=postgres_11&fiddle=9dbdd6cf405ae24c5e2a0798a732d389)*
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