title: substring in big query
body: <p>the following substring doesnt work in big query:</p>
  <p>substring(note.summary, charindex('[', note.summary)+1, charindex(']', note.summary) - charindex('[', note.summary) -1) as alpha ,</p>
  <p>with the error function not found: charindex
  Would you be able to help me out? I'm so confused</p>