Enhancement
Static SQL expressions should better be routed via DBHelper to be able to deal with the specifics of the different database implementations.
PostgreSQL for example pushes table and column names to lower case. For example
#!sql SELECT * FROM TEST_TABLE
is equivalent to
#!sql SELECT * FROM test_table
I.e. the statement fails if the table test_table does not exist.
There is a part of expressions that are routed through DBHelper and a part that are not. If they interact on the same table or column this can lead to problems, e.g. in PostgreSQL.
For completeness and consistency all SQL expressions should be routed through the DBHelper to avoid such errors.
Test
No test.