Combining Data with UNION for single column : Union « Set « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. Set
3. Union

SQL>
SQL> CREATE TABLE empExam (
  2     empID  INT NOT NULL,
  3     ExamID     INT NOT NULL,
  4     Mark       INT,
  5     Taken   SMALLINT,
  6     Comments   VARCHAR(255),
  7     CONSTRAINT PK_empExam PRIMARY KEY (empID, ExamID));
SQL>
SQL>
SQL>
SQL> CREATE TABLE dept (
  2     deptID INT NOT NULL PRIMARY KEY,
  3     empID    INT NOT NULL,
  4     ClassID      INT NOT NULL,
  5     EnrolledOn   DATE,
  6     Grade        INT);

Table created.

SQL>
SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (1,1,1,DATE '2002-09-23',62);

1 row created.

SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (2,1,2,DATE '2002-09-30',70);

1 row created.

SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (3,2,3,DATE '2003-09-23',51);

1 row created.

SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (4,2,5,DATE '2003-09-23',41);

1 row created.

SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (5,2,6,DATE '2003-09-23',68);

1 row created.

SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (6,3,4,DATE '2002-09-30',78);

1 row created.

SQL> INSERT INTO dept (deptID,empID,ClassID,EnrolledOn,Grade) VALUES (7,3,7,DATE '2002-09-30',80);

1 row created.

SQL>
SQL>
SQL> SELECT empID
  2     FROM empExam
  3     WHERE Mark < 40
  4  UNION
  5  SELECT empID
  6     FROM dept
  7     WHERE GRADE < 40
  8  ORDER BY empID;

     EMPID
----------
         2

1 row selected.

SQL>
SQL>
SQL> drop table empExam;

Table dropped.

SQL> drop table dept;

Table dropped.