FULL OUTER JOIN
A FULL OUTER JOIN in SQL is a type of join that combines rows from two or more tables based on a specified condition, and includes all rows from both the left (or first) and right (or second) tables. If there is no match, NULL values are filled in for columns from the table where no match is found.
My SQL Doesn't support Full Outer Join directly. So, we need to perform the left join and right join on two tables and then union their result.
Syntax
Follow the syntax below to perform the full outer join using the left join, right join and union.
SELECT * FROM table1 t1 LEFT JOIN table2 t2 ON t1.column_name = t2.column_name UNION SELECT * FROM table1 t1 RIGHT JOIN table2 t2 ON t1.column_name = t2.column_name;
Example
Consider two tables, students and grades:
Now, let's perform a FULL OUTER JOIN to retrieve information about all students and their grades:
SELECT s.student_id, s.student_name, g.grade
FROM Students s
LEFT JOIN Grades g ON s.student_id = g.student_id
UNION
SELECT g.student_id, s.student_name, g.grade
FROM Students s
RIGHT JOIN Grades g ON s.student_id = g.student_id;
Result
In this example, the FULL OUTER JOIN ensures that all students from the students table and all grades from the grades table are included in the result set. The rows that have no corresponding match in the other table display NULL values for columns from that table.
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