Hi,
In Internet i have read the collection Definition as

A collection is an ordered group of elements, all of the same type. It is a general concept that encompasses lists, arrays, and other datatypes used in classic programming algorithms. Each element is addressed by a unique subscript.

But when we define a collection with rowtype%tablename for example

Type type1 table of emp%rowtype;

,
how can we say that collection is a group of elements of same type. i'm confused with the statement.

So what's the issue in understanding the definition, it is perfect.

A composite data type stores values that have internal components. You can pass entire composite variables to subprograms as parameters, and you can access internal components of composite variables individually. Internal components can be either scalar or composite. You can use scalar components wherever you can use scalar variables. PL/SQL lets you define two kinds of composite data types, collection and record. You can use composite components wherever you can use composite variables of the same type.

In a collection, the internal components always have the same data type, and are called elements
. . .

Lalit Kumar B wrote on Fri, 22 November 2013 11:27

So what's the issue in understanding the definition, it is perfect.

No it is not perfect, as it does not specify in what context the term ordered has been used. The quoted definition says: "A collection is an ordered group of elements, all of the same type."

The definition by which OP got confused is a general statement about collections which are widely used.

A short definition of collections will not completely answer OP's confusion

OP must go through the entire concept explained in the manual. And, as a general concept, I still believe the definition is good.

Then both of you may want to have a look at the link I posted.

But when we define a collection with rowtype%tablename...
how can we say that collection is a group of elements of same type. i'm confused with the statement.

It has to be of same type in each group of elements. When you use %ROWTYPE, you have multiple ordered groups of elements, each group MUST have elements of same type. Don't get confused between an entire collection and each group of elements.

A short definition of collections will not completely answer OP's confusion, OP must go through the entire concept explained in the manual. And, as a general concept, I still believe the definition is good.

Type type1 table of emp%rowtype;