21jansession.md

Joins

Inner join

 select first_name, dept_name from employees inner join departments on employees.dept_id = departments.dept_id where salary < 15000 order by dept_name; 

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left join

select employee_id, first_name from employees left join departments on employees.dept_id = departments.dept_id where salary < 10000;

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right join

select employee_id, first_name, dept_name from employees right join departments on employees.dept_id = departments.dept_id where salary between 3000 and 20000 order by employee_id; 

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Cross join

select employee_id, first_name from employees cross join departments;

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full join

 select employee_id, first_name, dept_name from employees full join departments on employees.dept_id = departments.dept_id;
 

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ENUM

create type mood as ENUM ('sad', 'ok', 'good');

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OPERATIONS

UNION

select * from employees UNION select * from departments;

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INTERSECT

select * from employees INTERSECT select * from departments;

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UNION ALL

select * from employees UNION ALL select * from departments;

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EXCEPT

select * from employees EXCEPT select * from departments;