I’ll admit I didn’t test dataview queries 
, I was speaking more generally… and I always forget about undefined 
…
On the other hand, while writing this, I’ve tested this query :
```dataview
TABLE check
WHERE contains(file.frontmatter, "check") AND check != true
```
… check being a checkbox in Properties which seems to return the appropriate notes when check is blank or false (but finds nothing if check is true).
Don’t get me wrong though, I have nothing against having false as a default value for checkboxes 
.