SQL
SQL is a load language that is used for defining load steps that run SQL in the target database instance. This is main type of load step language to be used. What kind of SQL is expected to be used depends on load type and load step type.
See also:
Notes
SQL used in steps should be thought so that data is transformed in the target db instance. Usually this means that plain selects are not used but usually INSERT, MERGE etc. clauses are used to store result back to db tables etc.
Plain SELECT clauses are used in certain use cases e.g.
VIEW definitions
SMOKE load steps
GATEKEEPER load steps
Even in those cases (excluding VIEW definitions) it might be beneficial to think through SELECT so that it is optimal because ADE does not typically need actual data from customer database instance but very often something like information of existence of result rows is enough for use case like SMOKE and GATEKEEPER.