MySQL SQLLesson 28Free preview

MySQL Joins

This lesson is part of MySQL · All levels

Summary

JOIN is used to combine rows of two or more tables based on the relationships between columns, usually foreign keys versus primary keys. With JOIN, separate data in multiple tables can be displayed as a single result set without having to store it twice. MySQL provides several types of JOIN, and the type option determines which lines remain even if the pair does not exist.

Key points

JOIN combines two rows of tables via the ON condition on the relation column
The ON condition specifies how to match the line, e.g. s.id_kelas = k.id
Type JOIN (INNER, LEFT, RIGHT, CROSS, self) determines which line to join
Use a table alias to keep the combined query concise and unambiguous

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