Restrictions with the Collection-Expression Format

When you use the collection-expression format, certain restrictions apply:

A collection-derived table is read-only.
- It cannot be the target of INSERT, UPDATE, or DELETE statements.
  To perform insert, update, and delete operations, you must use the collection-variable format.
- It cannot be the underlying table of an updatable cursor or view.
In the FROM clause of the SELECT statement, the CALL keyword of SPL cannot precede the TABLE keyword of a table expression.
If the collection is a LIST data type, the resulting collection-derived table does not preserve the order of the elements in the LIST.
The underlying collection expression cannot evaluate to NULL.
The collection expression cannot contain a reference to a collection on a remote database server.
The collection expression cannot contain column references to tables that appear in the same FROM clause. That is, the collection-derived table must be independent of other tables in the FROM clause.
For example, the following statement returns an error because the collection-derived table, TABLE (parents.children), refers to the parents table, which is also referenced in the FROM clause:
```
SELECT COUNT(*)
   FROM parents, TABLE(parents.children) c_table
   WHERE parents.id = 1001;
```
To counter this restriction, you might write a query that contains a subquery in the Projection clause:
```
SELECT (SELECT COUNT(*)
      FROM TABLE(parents.children) c_table)
   FROM parents WHERE parents.id = 1001;
```