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An SQL LEFT join is a type of SQL join. This join returns all tables in a given "left" column and the corresponding rows that match a particular condition in the "right" column .
In many cases, when writing a query in SQL, it is sufficient to focus on a single table. However, there are many situations where you will need to query two or more tables at the same time. In this situation, you will want to create a result that combines information from both tables.
In SQL, this is called a join. Joins allow you to get information from multiple tables and combine the result into a joined table. For example, you can join the employee and department tables to get the department name for each employee.
In this tutorial, we’ll look at one type of join in SQL: the LEFT JOIN. We will see where LEFT JOIN are useful and how you can use them in your SQL queries.
SQL LEFT JOIN
SQL LEFT JOIN returns all records of a "left" table statement specified in the query. Match the values ‚Äã‚Äãin this array based on your conditions to a " straight " array . All matches are returned in addition to all records in the " left " table bar . _LEFT JOIN_s are a type of SQL outer join .
For example, you can use a left join to get a list of department names for each employee. This would allow you to see all employees even if they do not have an assigned department.
The basic syntax for a LEFT JOIN operation is as follows:
We start our join with a SQL SELECT statement . The table in the FROM statement is our "left" table . We therefore use the keyword LEFT JOIN. This allows us to specify a "right" table .