When working with SQL joins, it is common to retrieve multiple records that have duplicate values in one or more columns. However, there may be scenarios where you want to retrieve only distinct values from a specific column or set of columns. In such cases, you can use the SELECT DISTINCT statement along with joins.

Syntax

The syntax for using SELECT DISTINCT with joins is similar to the regular join syntax. Here’s an example:

SELECT DISTINCT column_name(s)
FROM table1
JOIN table2 ON join_condition

Example

Let’s consider a scenario where you have two tables: students and courses. The students table contains information about students, including their names and student IDs. The courses table contains information about different courses, including the course names and the student IDs of the students enrolled in each course.

To retrieve the distinct course names for all enrolled students, you can use the SELECT DISTINCT statement with a join:

SELECT DISTINCT courses.course_name
FROM students
JOIN courses ON students.student_id = courses.student_id

In this example, the DISTINCT keyword ensures that only unique course names are returned, eliminating any duplicate values. The JOIN condition connects the two tables based on the student_id column.

Conclusion

Using SELECT DISTINCT with joins allows you to retrieve only unique values from a specific column or set of columns when working with multiple tables. By incorporating this syntax in your SQL queries, you can filter out duplicate records and obtain the distinct results you desire.

#SQL #SELECT #distinct #joins