![]() To join these two tables and obtain the information we need for analysis, use the following SQL query: Here are the customers and sales tables from our bookstore. ![]() In this case, we want the result to include ALL customers–both active and inactive–by joining the data about our customers with the data about recent sales. Imagine that we run an online bookstore, and we want to compare the customers with orders in the last 6 months with those who were inactive during the same period. Alternatively, use a column from the second table that is fully populated with no NULL values, if there is one. ![]() However, first make sure that your second table doesn’t have records with NULL values in all columns except for the common field used for joining. In this case, you can add a WHERE clause to the query to select, from the result of the join, the rows with NULL values in all of the columns from the second table. First, it is very useful for identifying records in a given table that do not have any matching records in another. The LEFT JOIN is frequently used for analytical tasks. If you want more information on SQL joins, check out this comprehensive guide. The general syntax for a LEFT JOIN is as follows: If a record from the right table is not in the left, it will not be included in the result. This implies that, if a specific row is present in the left table but not in the right, the result will include this row but with a NULL value in each column from the right. In contrast, a LEFT JOIN in SQL returns all records (or rows) from the left table and only the matched records (or rows) from the right. You might remember that an INNER JOIN returns only the records that are in both tables. Let’s start by reminding ourselves what a LEFT JOIN is and how to use it. It is the most complete practical review of SQL JOINs available on the Internet. It contains over 90 hands-on exercises that cover simple 2-table joins, joining multiple tables, LEFT JOIN, FULL JOIN, and many more. The best way to practice different types of joins is our interactive SQL JOINs course. In this article, I will go through some examples to demonstrate how to LEFT JOIN multiple tables in SQL and how to avoid some common pitfalls when doing so. Can you LEFT JOIN three tables in SQL? Yes, indeed! You can use multiple LEFT JOINs in one query if needed for your analysis.
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