What is a LEFT JOIN and when is it used?

< 1 min read

A LEFT JOIN returns all records from the left table and matching records from the right table.
If there is no match, the right-side columns return NULL.
It is used when we want to keep all primary records even if related data is missing.
In my project, we used LEFT JOIN between customers and orders.
This helped identify customers who had not placed any orders.
It is useful for gap analysis and completeness checks.
LEFT JOIN ensures no loss of key business records during extraction.

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