You can use an ANSI-compliant SQL statement to generate a mapping in the Developer tool.
The Developer tool can generate a mapping from a standard SELECT query. For example:
SELECT column_list FROM table-name
[WHERE clause]
[GROUP BY clause]
[HAVING clause]
[ORDER BY clause]
If the SELECT SQL statement contains a correlated subquery, the query is valid if it is possible to flatten or rewrite the query as a single standard query.
ANSI SQL does not support some datatypes. For example, if the query requests results from a data source where one of the columns has the type timeStampTZ, the SQL is not valid.