Forum OpenACS Development: change in pg interpretation of not equal <>
It looks like pg has changed how it interprets the not equal <> for 9.x and late 8.2+ versions.
Now PG is sql compliant by ignoring comparisons where the value is null.
In earlier versions iirc, the null results were included if since they didn't match the comparison value. At least that's how it worked on my machine
Grepping, I see openacs has a few of these in sql.
Just mentioning it in case there should be checks for subtle changes in query results in acs-core.