Define each of the following terms:
- data definition language
- data manipulation language
- referential integrity constraint
- relational DBMS (RDBMS)
- schema
(a)
Define Data Definition Language.
Explanation of Solution
Data Definition language (DDL) is a computer language which is used for creating and modifying databases and schemas. The commonly used DDL commands are CREATE, ALTER, and DROP.
- CREATE command is used to create a new table with the following syntax
- ALTER command is used to modify the existing table. The syntax is:
- DROP command is used to delete a table. The syntax is:
Create table: Table name (Column definitions).
Alter table: Table name add new column.
Drop table: Table name
(b)
Define Data Manipulation Language.
Explanation of Solution
Data Manipulation Language is a computer language used in data structures to modify the data in the databases. The most commonly used data manipulation commands are INSERT, DELETE and UPDATE.
- INSERT command is used to add records in the database. The syntax for INSERT command is:
- DELETE command is used to delete records from the table according to the condition. Syntax is:
- UPDATE command is used to update the records in the database. Syntax is:
Insert into table Table name (columns) values (values)
Delete from table Table name where (condition)
Update Table name set (column = value) where (condition)
(c)
Define referential integrity constraint
Explanation of Solution
Refential Integrity constraint is the concept used in a relational database which ensures that the tables in the database are in a consistent state. This statement means that if there is any foreign key used in the database, it must be agreed with the primary key which is referenced from that foreign key. Any changes in the primary key must be updated in the foreign key as well.
(d)
Define Relational DBMS
Explanation of Solution
Relational Database Management System (RDBMS) is a type of DBMS which is used for the data stored in relational databases in the form of tables (combination of rows and columns). RDBMS is mainly used to store the data related to manufacturing, finance, logistic, and other applications. It uses SQL commands to access the databases.
(e)
Define Schema
Explanation of Solution
Schema is a structure or architecture of the database which is supported by the DBMS. It is considered as the blueprint of how the database is constructed. The schema is stored in the data dictionary generally by the database. It defines the objects in the databases.
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