How to make a calculated column blank if other columns doesnt have any values?

Question

This is my format in the calculated formula:

=TEXT([Column2]-[Column1];"hh:mm:ss")

I have value "2018-12-13 10:10:23" in Column1 but when Column2 is blank the calculated column shows "10:10:23" based of Column1.

Is there anyway to make it blank or say some text instead?

Tried this code in calculated column but with no success:

=IF(ISBLANK([Column2]);"no value";)=TEXT([Column2]-[Column1];"hh:mm:ss")

Answer 1

IF has three parts, condition, result if true, result if false.

=IF( a>b, "a is greater", "a is not greater" )

So:

=IF( ISBLANK(Column2); "no value"; TEXT(Column2-Column1;"hh:mm:ss") )

or

=IF( ISBLANK(Column2); ""; TEXT(Column2-Column1;"hh:mm:ss") )