LEFT JOIN

The LEFT JOIN command combines matching rows with rows from the left-side table.

Syntax

SELECT column_name(s)
FROM table_1
LEFT JOIN table_2
  ON table_1.column_name = table_2.column_name;

Every row in the left table is returned in the result set. If the join condition is not met, then NULL values are used to fill in the columns from the right table.

Example

To create a result set of every row in the students table combined with the transfer_data table where student IDs match. And if the join condition is not met, then NULL values are used to fill in the columns from the transfer_data table.

SELECT
  students.first_name,
  students.last_name,
  students.overall_gpa,
  transfer_data.overal_gpa
FROM students
LEFT JOIN transfer_data
  ON students.student_id = transfer_data.student_id;

The result set will only include last name, first name, and both GPAs.