I get the following error that a shared is not found, even though it exists, is in the library path, and ldd knows where the file is: ...

The EXISTS condition is an operator whose right operand is a subquery. The result of an EXISTS condition is true if the subquery resolves to at least one row. The result of a NOT EXISTS condition is ...

Null means "undefined" in SQL, so numerous online services don't think Christopher Null exists.