25.  What is DDL (Data Definition Language)?

A data base schema is specifies by a set of definitions expressed by a special language called DDL.

 

26.  What is VDL (View Definition Language)?

It specifies user views and their mappings to the conceptual schema.

 

27.  What is SDL (Storage Definition Language)?

This language is to specify the internal schema. This language may specify the mapping between two schemas.

 

28.  What is Data Storage – Definition Language?

The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.

 

29.  What is DML (Data Manipulation Language)?

This language that enable user to access or manipulate data as organised by appropriate data model.

Ø      Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.

Ø      Non-Procedural DML or High level:  DML requires a user to specify what data are needed without specifying how to get those data.

 

31.  What is DML Compiler?

It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

 

32.  What is Query evaluation engine?

It executes low-level instruction generated by compiler.

 

33.  What is DDL Interpreter?

It interprets DDL statements and record them in tables containing metadata.

 

34.  What is Record-at-a-time?

The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.

 

35.  What is Set-at-a-time or Set-oriented?

The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.

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