The Oracle SELF Join query is used to join a table with itself, i,e, each row is combined with itself and every other rows of the table.
SELECT A.columns, B.columns FROM table_1 A, table_1 B WHERE A.common_filed = B.common_field;
STUDENT_ID STUDENT_NAME STUDENT_AGE 1 Joy 20 2 Smiley 19 3 Happy 21 4 James 22 5 Bond 25
SELECT A.student_id, A.student_name, B.student_age FROM students A, students B WHERE A.student_age < B.student_age;
STUDENT_ID STUDENT_NAME STUDENT_AGE 1 Joy 21 1 Joy 22 1 Joy 25 2 Smiley 20 2 Smiley 21 2 Smiley 22 2 Smiley 25 3 Happy 22 3 Happy 25 4 James 25
The 'students' is an already existing table. After the joining, the selected fields of the rows of table A and table B will be displayed for which the student_age in table A is less than that in table B.