1 EXISTS(n)
Returns TRUE if the nth element in a collection exists; otherwise returns FALSE.
2 COUNT
Returns the number of elements that a collection currently contains.
3 LIMIT
Checks the Maximum Size of a Collection.
4 FIRST
Returns the first (smallest) index numbers in a collection that uses integer subscripts.
5 LAST
Returns the last (largest) index numbers in a collection that uses integer subscripts.
6 PRIOR(n)
Returns the index number that precedes index n in a collection.
7 NEXT(n)
Returns the index number that succeeds index n.
8 EXTEND
Appends one null element to a collection.
9 EXTEND(n)
Appends n null elements to a collection.
10 EXTEND(n,i)
Appends n copies of the ith element to a collection.
11 TRIM
Removes one element from the end of a collection.
12 TRIM(n)
Removes n elements from the end of a collection.
13 DELETE
Removes all elements from a collection, setting COUNT to 0.
14 DELETE(n)
Removes the nth element from an associative array with a numeric key or a nested table. If the associative array has a string key, the element corresponding to the key value is deleted. If n is null, DELETE(n) does nothing.
15 DELETE(m,n)
Removes all elements in the range m..n from an associative array or nested table. If m is larger than n or if m or n is null, DELETE(m,n) does nothing.
其他：
Oracle 目前不支持多维集合 ，三个都是一维的
