Updating nested table
Within the database, nested tables can be considered one-column database tables.
Oracle stores the rows of a nested table in no particular order.
PL/SQL nested tables are like one-dimensional arrays.
You can model multi-dimensional arrays by creating nested tables whose elements are also nested tables.
Nested tables can be sparse: you can delete arbitrary elements, rather than just removing an item from the end.
Nested table data is stored out-of-line in a store table, a system-generated database table associated with the nested table.
It is a general concept that encompasses lists, arrays, and other familiar datatypes.
But you might find it impractical to store and retrieve large numbers of elements this way.You can define collection types in a procedure, function, or package.You can pass collection variables as parameters, to move data between client-side applications and stored subprograms.The most efficient way to pass collections to and from the database server is to use anonymous PL/SQL blocks to bulk-bind input and output host arrays to associative arrays.Varrays are a good choice when the number of elements is known in advance, and when the elements are usually all accessed in sequence.