ORA-08712
Query block nesting limit exceeded (maximum allowed level of nesting = string).
Cause
SQL assertions are not supported when there are more than the maximum allowed level of nesting of query blocks. Following is an example of two-level nesting assertion: CREATE ASSERTION ASRT_LEVEL_2 CHECK (NOT EXISTS(SELECT * FROM t1 WHERE NOT EXISTS(SELECT 1 FROM t2 WHERE t1.c1=t2.c2)
Action
Use fewer levels of nesting.