DBMS Concepts General Introduction
Hi Friends!!!Greetings to Everyone!!!!
I am posting this general introduction about the ADO.NET concepts in short description, based on .NET point of view.
–Microsoft SQL Server 2005/2008
–File System Concepts — Drawback is Redundancy Problem
–DBMS Concept is evolved.
- Relation Schema — refers to the tables
- Record — value of particular field
- RecordSet — Entire row values of particular tuple
- Attribute — refers to the column
- Tuple — refers to the row values
- Instance — refers to the database object or instance
Main Properties of DBMS:
A – Atomicity — Either all transactions or none of the transactions executed
C – Consistency — Updates has to be done parallel
I – Isolation — All the transactions executed as an isolated manner [Separate]
D – Durability — Once the changes has been made, it cant be undone
R – RETRIEVE [SELECT]
U – UPDATE
D – DELETE
Statements in ADO.NET:
1. DDL [Data Definition Language]
2. DML [Data Manipulation Language]
3. DCL [Data Control Language]
4. TCL [Transaction Control Language]
5. DQL [Data Query Language]
- Statements which are affecting the physical structure of database objects.
- Statements which are performing manipulations of records on the database objects.
- Statements which are retrieving the recordset values from database objects.
- Statements that are used to set and reset the access privileges.
- Statements that are used to perform operations based on the transactions.
1. Key Constraint
—Super Key — Combination of fields which are having ability to become primary key
—Candidate Key — Minimal subset of super key is called as candidate key
—Primary Key — One from candidate key is called as primary key
–which is used to uniquely identify the recordset
—Alternate or Secondary Key — Remaining in the candidate keys [Candidate Key – (Minus) Primary Key]
—Composite Key — [Super Key-Candidate Key]
—Foreign Key — Primary key of another table
2. Not Null Constraint — will not allow null values, but will allow the duplicate values.
3. Unique Constraint — will not allow duplicate values, but will allow the null value once.
4. Check Constraint — will check the values to be in the specified range. Example: For Gender, only the possible values are Male/Female. Check Constraint will not allow any other values.
5. Default Constraint — If the value is not supplied while inserting a column values, default value will be inserted.