SQL how to collapse multiple columns into two columns, one for column heading and the second for column value

Question

If the input data looks like this:

Key	Col1	Col2	Col3	Col4
keyA	val1	val2	val3	val4
keyB	val1	val2	val3	val4

How can I convert it to look like this?

Key	ColTitle	ColVal
keyA	Col1	val1
keyA	Col2	val2
keyA	Col3	val3
keyA	Col4	val4
keyB	Col1	val1
keyB	Col2	val2
keyB	Col3	val3
keyB	Col4	val4

Answer 1

One method is union all:

select key, 'Col1' as coltitle, col1 as colval
from t
union all
select key, 'Col2' as coltitle, col2 as colval
from t
union all
select key, 'Col3' as coltitle, col3 as colval
from t
union all
select key, 'Col4' as coltitle, col4 as colval
from t