ouput of a row as a column name
output of a inner query to used as a column name for outer query .
Eg. :
select x1 from table1
x1
---
H1
select h1 from table2
h1
----
1
2
3
0
Eg. :
select x1 from table1
x1
---
H1
select h1 from table2
h1
----
1
2
3