- Associative Arrays
- Nested Tables
Next you have nested tables. Indexes are numeric and start with 1. These start out as dense collections. But they could get sparse if you DELETE an item. This type of collection can be stored in a database. When you do that, the data for columns of this type is stored out of line. You can initialize the collection with a constructor. And you can define a collection of this type like TYPE my_nested_type IS TABLE OF VARCHAR2(4).
The VARRAY is like the nested table. It also has numeric indexes which start at 1. You can store collections of this type in a table. Unlike nested arrays, columns of this type in a database table have the collection stored inline. The result is better performance than nested tables in database tables. This collection type is always dense. While you can DELETE from a VARRAY, you must DELETE all items in the VARRAY. You can define a collection of this type like TYPE my_varray_type IS VARRAY(10) OF VARCHAR2(4).
Here are some functions that work on collections:
- EXTEND (nested table or VARRAY only)
- TRIM (nested table or VARRAY only)