Sql what's the difference between a left connection LEFT JOIN and a right connection RIGHT JOIN?

This article mainly introduces the sql left connection LEFT JOIN and right connection RIGHT JOIN what is the difference, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to know about it.

The difference between sql left join and right join is that the left join reads all the data of the left data table, even if the right data table has no corresponding data, while the right join reads all the data of the right data table, even if the left data table has no corresponding data.

Left connection:

Keyword: LEFT JOIN

Left table: books right table: articles

The left join reads all the data from the left data table, even if the right data table has no corresponding data. (if the data in two tables have the same part, only one is displayed)

Right connection:

Keyword: RIGHT JOIN

Left table: books right table: articles

The right join reads all the data from the data table on the right, even if the data table on the left has no corresponding data. (if the data in two tables have the same part, only one is displayed)

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