LEFT OUTER JOIN¶
Function¶
Join the left table with the right table and return all joined records of the left table. If no joined record is found, NULL will be returned.
Syntax¶
SELECT attr_expr_list FROM table_reference
LEFT OUTER JOIN table_reference ON join_condition;
Keyword¶
LEFT OUTER JOIN: Returns all joined records of the left table. If no record is matched, NULL is returned.
Precautions¶
The to-be-joined table must exist. Otherwise, an error is reported.
Example¶
To join the courseId from the student_info table to the courseId from the course_info table for inner join and return the name of the students who have selected course, run the following statement. If no joined record is found, NULL will be returned.
SELECT student_info.name, course_info.courseName FROM student_info
LEFT OUTER JOIN course_info ON (student_info.courseId = course_info.courseId);