oracle使用序列nextval, currval限制

同一层的SQL，使用序列，不允许有排序操作，不能有order by



Restrictions on Sequence Values You cannot use CURRVAL and NEXTVAL in the
following constructs:
■ A subquery in a DELETE, SELECT, or UPDATE statement
■ A query of a view or of a materialized view
■ A SELECT statement with the DISTINCT operator
■ A SELECT statement with a GROUP BY clause or ORDER BY clause
■ A SELECT statement that is combined with another SELECT statement with the
UNION, INTERSECT, or MINUS set operator
■ The WHERE clause of a SELECT statement
■ The DEFAULT value of a column in a CREATE TABLE or ALTER TABLE statement
■ The condition of a CHECK constraint
Within a single SQL statement that uses CURRVAL or NEXTVAL, all referenced LONG
columns, updated tables, and locked tables must be located on the same database.