Subqueries in the WHERE Clause: less than : Single Row Subquery « Query Select « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. Query Select
3. Single Row Subquery

SQL>
SQL> CREATE TABLE emp (
  2     empID      INT NOT NULL PRIMARY KEY,
  3     CourseID    INT NOT NULL,
  4     ProfessorID INT NOT NULL,
  5     SustainedOn DATE,
  6     Comments    VARCHAR(255));

Table created.

SQL> INSERT INTO emp (empID,CourseID,ProfessorID,SustainedOn,Comments) VALUES (1,1,1,DATE '2003-03-12','Hard');

1 row created.

SQL> INSERT INTO emp (empID,CourseID,ProfessorID,SustainedOn,Comments) VALUES (2,2,1,DATE '2003-03-13','Simple');

1 row created.

SQL> INSERT INTO emp (empID,CourseID,ProfessorID,SustainedOn,Comments) VALUES (3,3,2,DATE '2003-03-11','1 hour long');

1 row created.

SQL> INSERT INTO emp (empID,CourseID,ProfessorID,SustainedOn) VALUES (4,4,3,DATE '2003-03-18');

1 row created.

SQL>
SQL> SELECT empID, SustainedOn FROM emp
  2  WHERE SustainedOn <= (
  3     SELECT SustainedOn FROM emp WHERE empID = 5)
  4  ORDER BY SustainedOn DESC;

no rows selected

SQL>
SQL>
SQL> drop table emp;

Table dropped.