MySQL Tutorial/Select Query/UNION

UNION allows you to combine the results from different tables

mysql>
mysql> CREATE TABLE Employee(
    ->     id            int,
    ->     first_name    VARCHAR(15),
    ->     last_name     VARCHAR(15),
    ->     start_date    DATE,
    ->     end_date      DATE,
    ->     salary        FLOAT(8,2),
    ->     city          VARCHAR(10),
    ->     description   VARCHAR(15)
    -> );
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql> create table job (
    ->   id         int,
    ->   title      VARCHAR(20)
    -> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql>
mysql> create table duty (
    ->   id         int,
    ->   task       VARCHAR(20)
    -> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->              values (1,"Jason",    "Martin",  "19960725",  "20060725", 1234.56, "Toronto",  "Programmer");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(2,"Alison",   "Mathews",  "19760321", "19860221", 6661.78, "Vancouver","Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(3,"James",    "Smith",    "19781212", "19900315", 6544.78, "Vancouver","Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(4,"Celia",    "Rice",     "19821024", "19990421", 2344.78, "Vancouver","Manager");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(5,"Robert",   "Black",    "19840115", "19980808", 2334.78, "Vancouver","Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(6,"Linda",    "Green",    "19870730", "19960104", 4322.78,"New York",  "Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(7,"David",    "Larry",    "19901231", "19980212", 7897.78,"New York",  "Manager");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(8,"James",    "Cat",     "19960917",  "20020415", 1232.78,"Vancouver", "Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into job (id, title) values (1,"Tester");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (2,"Accountant");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (3,"Developer");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (4,"Coder");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (5,"Director");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (6,"Mediator");
Query OK, 1 row affected (0.02 sec)
mysql> insert into job (id, title) values (7,"Proffessor");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (8,"Programmer");
Query OK, 1 row affected (0.00 sec)
mysql> insert into job (id, title) values (9,"Developer");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into duty (id, task) values (1,"Test");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values (2,"Calculate");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values (3,"Program");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values (4,"Test");
Query OK, 1 row affected (0.02 sec)
mysql> insert into duty (id, task) values (5,"Manage");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values (6,"Talk");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values  (7,"Speak");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values (8,"Shout");
Query OK, 1 row affected (0.00 sec)
mysql> insert into duty (id, task) values  (9,"Walk");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from job;
+------+------------+
| id   | title      |
+------+------------+
|    1 | Tester     |
|    2 | Accountant |
|    3 | Developer  |
|    4 | Coder      |
|    5 | Director   |
|    6 | Mediator   |
|    7 | Proffessor |
|    8 | Programmer |
|    9 | Developer  |
+------+------------+
9 rows in set (0.00 sec)
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql> select * from duty;
+------+-----------+
| id   | task      |
+------+-----------+
|    1 | Test      |
|    2 | Calculate |
|    3 | Program   |
|    4 | Test      |
|    5 | Manage    |
|    6 | Talk      |
|    7 | Speak     |
|    8 | Shout     |
|    9 | Walk      |
+------+-----------+
9 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> SELECT title
    -> FROM job
    -> UNION
    -> SELECT task
    -> FROM duty;
+------------+
| title      |
+------------+
| Tester     |
| Accountant |
| Developer  |
| Coder      |
| Director   |
| Mediator   |
| Proffessor |
| Programmer |
| Test       |
| Calculate  |
| Program    |
| Manage     |
| Talk       |
| Speak      |
| Shout      |
| Walk       |
+------------+
16 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> drop table duty;
Query OK, 0 rows affected (0.00 sec)
mysql> drop table job;
Query OK, 0 rows affected (0.02 sec)
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>

UNION Joins

Union Joins allow the results of two queries to be combined into one outputted result set.

Union Join is done by having the 2 (or more) queries glued together by the UNION operator.

SELECT <fields>
 FROM <table>
 WHERE <condition>
UNION
SELECT <fields>
 FROM <table>
 WHERE <condition>