SELECT SINGLE selects only one record, even if more records exist that
meet the specified selection criteria.
Therefore SELECT SINGLE should only be used in the following
situations:
- a unique selection is specified in the WHERE clause;
- you do only want to know if record(s) do or do not exist that meet
the selection criteria.

Another possible use of SELECT without ENDSELECT is:
SELECT INTO TABLE.
This variant is always faster than SELECT with ENDSELECT, because the
database is accessed only once, whereas SELECT ... ENDSELECT accesses
the database multiple times.
This does not mean that SELECT INTO TABLE should always be used instead
of SELECT ... ENDSELECT.
This depends on the amount of records read. A very large internal table
will quickly deteriorate performance.
 

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