There is a requirement to convert column data into rows.
Consider the country table with data as follows
Table has 4 columns (country , value1,value2,value3)
NZ 50 60 70
AUS 110 120 130
The output should be displayed in following manner
select country, value1 as value from T_country
select country, value2 as v from T_country
select country, value3 as v from T_country;
There might be various approaches to this problem.Union was found out to be efficient and served the purpose.