Relational Database Management System

1. Relational Database Management System

2. What is DBMS? A Database Management System (DBMS) is a set of computer programs that controls the creation, maintenance, and the use of the database in a computer platform or of an organization and its end users. A DBMS is a system software package that helps the use of integrated collection of data records and files known as databases. It provides facilities for controlling data access, enforcing data integrity, managing concurrency controlled, restoring database. What is Database? A collection of information organized in such a way that a computer program can quickly select desired pieces of data. Collection of data treated as a single unit. Traditional databases are organized by fields, records, and files. A field is a single piece of information ; a record is one complete set of fields; and a file is a collection of records.

3. Database Integrity? Security constraint guard against accidental or malicious tampering with data, whereas integrity constraint ensure that any properly authorized access, alteration, deletion, or insertion of the data in the database does not changed the consistency and validity of the data. This required for guarding against invalid database operation. What is concurrency control? Concurrency control in DBMS ensures that database transactions are performed concurrently without the violating the data integrity of a database.

4. What is Relational database management system(RDBMS)? RDBMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables. RDBMS is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd. • What is the difference between DBMS & RDBMS? In DBMS all the tables are treated as different entities. There is no relation established among these entities. But the tables in RDBMS are dependent and the user can establish various integrity constraints on these tables so that the ultimate data used by the user remains correct.

5. The main advantage of an RDBMS is that it checks for referential integrity. You can set the constraints in an RDMBS such that when a particular record is changed, related records are updated/deleted automatically. Example of DBMS are FoxPro, MsAcess Example of RDBMS are SQL,PL/SQL DBMS is a single user system where RDBMS is a multiuser system.

6. Difference between oracle & SQL? 1.Oracle is made up of a set of processes running in your operating system. These processes manage how data is stored and how it is accessed. Oracle is a program that is running in the background, maintaining your data for you and figuring out where it should go on your hard drive. SQL is a oracle tool which is used to access the data. SQL allows you to SELECT your data, INSERT new records, UPDATE existing records and DELETE records you want to get rid of. • Difference between SQL and PL/SQL? 1.SQL is the structured query language which is used to access the data from the database. PL/SQL is the procedure language extension to the SQL. PL/SQL is a programming language like C, Java or Pascal. In the Oracle world, there is no better way to access your data from inside a program.

7. Some of Oracle's tools to access the database and create programs are: SQL*Plus has a command line interface. With it, you can access the database and write stored procedures, you can run SQL commands to retrieve data and you can run scripts of either SQL, PL/SQL or built-in SQL*Plus commands, or a mixture of those three things. Oracle Developer is a 4GL GUI application Builder. With Developer, you can create forms, reports, and graphics. Oracle*Forms and Oracle*Reports are two components of Oracle Developer. Earlier versions created client-server applications, but the more recent versions create web applications that run under the Oracle Application Server (OAS). OAS is a web-based application server sold by Oracle. OAS is licensed separately and is very expensive (as are its closed source competitors). The current version is OAS 10g.

8. HTML DB is a fairly new application builder geared toward web development Oracle Enterprise Manager (OEM) is the Enterprise GUI tool to manage the database. From this tool, you can perform any action in the database that is required. This tool is primarily used for administration but can also be provided to developers for application tuning and monitoring. In Oracle 10g, OEM also provides Grid control.

9. Codd’s Rule: Rule 1 : The information Rule. "All information in a relational data base is represented explicitly at the logical level and in exactly one way - by values in tables.“ Rule 2 : Guaranteed access Rule. "Each and every datum (atomic value) in a relational data base is guaranteed to be logically accessible by resorting to a combination of table name, primary key value and column name."

10. Rule 3 : Systematic treatment of null values. "Null values (distinct from the empty character string or a string of blank characters and distinct from zero or any other number) are supported in fully relational DBMS for representing missing information and inapplicable information in a systematic way, independent of data type.“ Rule 4 : Dynamic on-line catalog based on the relational model. "The data base description is represented at the logical level in the same way as-ordinary data, so that authorized users can apply the same relational language to its interrogation as they apply to the regular data.“

11. Rule 5 : Comprehensive data sub-language Rule. "A relational system may support several languages and various modes of terminal use (for example, the fill-in-the-blanks mode). However, there must be at least one language whose statements are expressible, per some well-defined syntax, as character strings and that is comprehensive in supporting all the following items Data Definition View Definition Data Manipulation (Interactive and by program). Integrity Constraints Authorization.

12. Rule 6 : .View updating Rule "All views that are theoretically updatable are also updatable by the system.“ Rule 7 : High-level insert, update and delete. The system must support set-at-a-time insert, update, and delete operators. This means that data can be retrieved from a relational database in sets constructed of data from multiple rows and/or multiple tables. This rule states that insert, update, and delete operations should be supported for any retrievable set rather than just for a single row in a single table.

13. Rule 8 : Physical data independence. "Application programs and terminal activities remain logically unimpaired whenever any changes are made in either storage representations or access methods.“ or Changes to the physical level (how the data is stored, whether in arrays or linked lists etc.) must not require a change to an application based on the structure. Rule 9 : Logical data independence. "Application programs and terminal activities remain logically unimpaired when information-preserving changes of any kind that theoretically permit un-impairment are made to the base tables.“

14. Changes to the logical level (tables, columns, rows, and so on) must not require a change to an application based on the structure. Note: Logical data independence is more difficult to achieve than physical data independence. Rule 10 : Integrity independence. "Integrity constraints specific to a particular relational database must be definable in the relational data sub-language and storable in the catalog, not in the application programs.“ The database catalog of a database instance consists of metadata in which definitions of database objects such as base tables, views (virtual tables), synonyms, value ranges, indexes, users, and user groups are stored

15. If a column only accepts certain values, then it is the RDBMS which enforces these constraints and not the user program, this means that an invalid value can never be entered into this column, whilst if the constraints were enforced via programs there is always a chance that a buggy program might allow incorrect values into the system. Rule 11 : Distribution independence. "A relational DBMS has distribution independence." The RDBMS may spread across more than one system and across several networks, however to the end-user the tables should appear no different to those that are local.

16. Rule 12 : Non-subversion Rule. "If a relational system has a low-level (single-record-at-a-time) language, that low level cannot be used to subvert or bypass the integrity Rules and constraints expressed in the higher level relational language (multiple-records-at-a-time)."