Improve a couple of sql/json error messages

Andrew Dunstan <andrew@dunslane.net>

Commit: 4cd8717af3f0345c758d46fea06fb390b4d593f2
Author: Andrew Dunstan <andrew@dunslane.net>
Date: 2022-04-14T14:26:29Z
Releases: 15.0
Improve a couple of sql/json error messages

Fix the grammar in two, and add a hint to one.

Files