What I imagine is a tool on which you can select your SQL database (ideally any of the RDBMS but if it is limited preferably PostgreSQL). In said tool administrator can create query and result forms that query the selected table(s). The administrator defines which fields are searchable and which are displayed in the results. Users can then use the forms for querying the database.
Does such a web application exist?
The application should be easy to use for users and web-based. It should be a search tool and not a database admin tool (eg. not pgAdmin). The search forms are defined by administrator and users have to use them and get displayed the search results.