I have question how to replace whitespace with _ using notepad++ regex between [] characters
Example :
sl.[Posting date] AS TIME,
Find what: [.+(\s)+.+]
Replace with: _
Also don't forget to select Regular expression
radio button in Search mode
section.
Update:
Ok, I have one solution but it's dirty:
You need to perform several replacements to do that.
Find what: (\[.*)\s(.*\])
Replace with: \1_\2
Repeat using Replace all
until there will be no occurrences.