RDBMS interview questions and answers

Q11: What are the different Codd’s 12 rules for Relational databases?

Ans: Codd's 12 rules are a collection of thirteen rules developed by Edgar F. Codd (numbered zero to twelve): –

Rule 0 : The system must be qualified as a Relational, a Database, and a Management Systems.

Rule 1:  The information rule─ Every piece of data in the database must be represented uniquely, mostly by name values in column locations inside a distinct row of a table.

Rule 2:  The guaranteed access rule─ Ingressive data must be used in all cases. It states that every scalar value in the database must be accessible correctly/logically.

Rule 3:  Systematic treatment of null values─ Each tuple must be allowed to stay null by the DBMS.

Rule 4:  Active online catalog (database’s structure) based on the relational model─ The system must provide an online, relational, or other structure that is ingressive to authorized users via their regular queries.

Rule 5:  The comprehensive data sublanguage─ The system must help at least one relational language that:

  • 1. has a linear syntax
  • 2. Which may be utilized interactively as well as within application applications,
  • 3. It enables data definition and manipulation activities (DDL and DML) and security and integrity restrictions, and transaction management procedures (begin, commit, and rollback).

Rule 6:  The view updating rule─ The system must upgrade any views that potentially improve.

Rule 7:  High-level insert, update, and delete: Insert, update, and delete the system must support operators.

Rule 8:  Physical data independence─ Modifying the physical level (how data is stored, utilizing arrays or linked lists, etc.) must not need a change to the program.

Rule 9:  Logical data independence─ Modifying the logical level (tables, columns, rows, etc.) must not change the application.

Rule 10:  Integrity independence─ Integrity restrictions must be recognized and cataloged independently from application programs.

Rule 11:  Distribution independence─ Users should not see the distribution of sections of a database to multiple sites.

Rule 12:  The nonsubversion rule─ If the system provides a low-level (i.e., records) interface, that interface cannot be exploited to undermine the system.

Q12: What Is Rdbms Kernel?

Ans: The kernel, software, and the data dictionary, which consists of the system-level data structures required by the kernel to operate the database, are two critical components of RDBMS design. An RDBMS may be thought of as an operating system (or group of subsystems) built to regulate data access; its major tasks are data storage, retrieval, and security. An RDBMS handles memory caches and paging, regulates locking for concurrent resource consumption, dispatches and schedules user requests, and manages space usage inside its table-space structures.

Q13: What Is Rowid?

Ans: The ROWID is a one-of-a-kind database-wide physical address for each row on each table. It is never changed once allocated (when the record is first entered into the database) until the row is removed or the table is discarded.

The ROWID is made up of three parts, the combination of which uniquely identifies the row's actual storage location.

  • The Oracle database file number containing the block with the rows.
  • The Oracle block address containing the row
  • The row included inside the block (because each block can hold many rows)

The ROWID is used internally in indexes to get rows with a certain key-value quickly. Application developers also use it in SQL queries to retrieve a row quickly once they know the ROWID.

Q14: Does Pl/SQL Support "overloading"? Explain

Ans: Overloading in PL/SQL refers to the idea of defining procedures and functions with the same name. PL/SQL does not simply look at the referred name to resolve a procedure or function call. The count and data kinds of formal parameters are also taken into account.

Before looking at globally specified packages or internal functions, PL/SQL tries to resolve any procedure or function calls in locally defined packages. You may use the dot notation to check that you are calling the correct method. Any procedure or function reference is fully qualified when the package name precedes it.

Q15: What Are Stored-procedures? And What Are The Advantages Of Using Them.

Ans: Database objects that perform a user-defined action are known as stored procedures. A stored procedure may include a collection of compound SQL statements. A stored procedure executes the SQL instructions, and the result is returned to the client. To decrease network traffic, stored processes are employed.