A scalar subquery can be specified as a parameterized value in the value list of a simple INSERT request, but Vantage always interprets it as a noncorrelated scalar subquery.
For example, the database processes the scalar subquery SELECT d2 FROM t2 WHERE a2=t1.a1 in the select list of the following INSERT request as if it were SELECT d2 FROM t2, t1 WHERE a2=t1.a1.
In other words, the database interprets t1 in the scalar subquery as a distinct instance of t1 rather than as the target table t1 of the insert operation.
INSERT INTO t1 VALUES (1,2,3 (SELECT d2 FROM t2 WHERE a2=t1.a1));