docs: fix query to be valid SQL by adding where

[jasongi]

Noticed this issue while looking into #39

[codecov[bot]]

Codecov Report

Merging #40 (d6aa70d) into master (e2a16ab) will not change coverage. The diff coverage is n/a.

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[samuelcolvin]

I'll try to get to this and #39 soon as well as fixing deps and pinning them.

[euri10]

would be better to use the Where() clause and Empty() imho, that would at least show an example, I often build queries this way