SQL join

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SQL Join

  • Join means that a table is connected with another table or other tables through a specific, mutual columns.

  • types:

  1. inner join
  2. left join
  3. outer join: left/right join & union
  4. right join

  • if you make a join on tables, write “(inner)/left/right join ~ on” in a query.

  • union: remove the duplicated data

  • if you make a join on three tables, you can write the names of three tables next to the reserved word “from”.