add example not exists query

[nicpottier]

No description provided.

[codecov-io]

Codecov Report

Merging #7 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #7   +/-   ##
=======================================
  Coverage   78.61%   78.61%           
=======================================
  Files           1        1           
  Lines         173      173           
=======================================
  Hits          136      136           
  Misses         21       21           
  Partials       16       16

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