MySQL

Introduction Of MySQL

Start with MySQL Server

Syntax In MySQL

Select In MySQL

Distinct In MySQL

Where In MySQL

And & Or In MySQL

Order By In MySQL

Insert Into In MySQL

Update In MySQL

Delete In MySQL

Injection In MySQL

Select Limit In MySQL

Like In MySQL

Wildcards In MySQL

Aliases In MySQL

Joins In MySQL

Inner Join In MySQL

Left Join In MySQL

Right Join In MySQL

Union In MySQL

Create DB In MySQL

Create Table In MySQL

DataTypes In MySQL

Normalization

Functions In MySQL

Keys & Level of Abstraction

Codd's Twelve Rules

MySQL subjective question

MySQL Interview question

MySQL Objective question

MySQL FAQS

RDMS FAQS

Oracle Interview Questions

It allow us to add one or more column from one or more table in a single output. It follow some conditions to perform they are:

1. Number of column should be equal in both sides.
2. Both the matched column should have some type of data.

Syntax for Union

SELECT columnname1, columnname2
FROM table1
UNION DISTINCT | ALL
SELECT columnname1, columnname2
FROM table2
[WHERE CLAUSE
ORDER BY CLAUSE]

Example

SELECT ocuptn, sex
FROM studptin
UNION
SELECT fname,age
FROM studinfo ;

Default value use in union is distinct.

Example

SELECT fname,age
FROM studinfo
UNION ALL
SELECT ocuptn, sex
FROM studptin ;

The full output can be shown by all in union condition.

Example

SELECT ocuptn, sex
FROM studptin
UNION 
SELECT fname,age
FROM studinfo 
WHERE age>23
ORDER BY ocuptn;

Include the where and order b y condition in the above code.

Example

( SELECT ocuptn, sex
FROM studptin )
UNION 
( SELECT fname,age
FROM studinfo )
ORDER BY 2,1;

The type of order define in terms of the second select column name define in the code.