DBMS Chapter Notes - Chapter 3: Data Definition Language, Data Manipulation Language, Unique Key
Document Summary
Ddl is data definition language which is used to define data structures. For example: create table, alter table are instructions in sql. Dml is data manipulation language which is used to manipulate data itself. For example: insert, update, delete are instructions in sql. It is used to create database schema and can be used to define some constraints as well. It is used to add, retrieve or update the data. It basically defines the column (attributes) of the table. It add or update the row of the table. Ddl does not use where clause in its statement. While dml uses where clause in its statement. Keys: keys play an important role in the relational database. It is used to uniquely identify any record or row of data from the table. It is also used to establish and identify relationships between tables. For example: in student table, id is used as a key because it is unique for each student.
