{"id":21725,"date":"2018-08-05T04:00:58","date_gmt":"2018-08-05T04:00:58","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=21725"},"modified":"2025-03-29T21:23:35","modified_gmt":"2025-03-29T15:53:35","slug":"sql-rdbms","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/sql-rdbms\/","title":{"rendered":"SQL RDBMS Concept – Features & Advantages"},"content":{"rendered":"

In this tutorial, we will be focusing on\u00a0 SQL RDBMS concepts.<\/p>\n

RDBMS stands for Relational Database Management System.<\/p>\n

RDBMS concepts are a basic requirement to understand SQL and all other modern database examples: MS Access, SQL, MS SQL Server, etc.<\/p>\n

It is a database management and organization system based on relational models and their principles. Let us now dive into the RDBMS concepts and master them with this tutorial.<\/p>\n

Demo Database<\/h3>\n

Let us first have a look at the database we will be using for this tutorial. We are using the DataFlair database.
\nQuery:<\/strong><\/p>\n

SELECT * FROM DataFlair;<\/pre>\n
Output:<\/strong><\/p>\n
\"SQL<\/a><\/p>\n
Here we can view the contents of the DataFlair database.<\/p>\n
Components of RDBMS<\/h3>\n
\"\"<\/a><\/p>\n
The major components of an RDBMS are as follows:<\/p>\n
1. RDBMS Table<\/h4>\n
Data in RDBMS is stored in objects called as tables. A table is a collection of records or tuples containing the values associated with the columns or attributes available in a table.<\/p>\n
Query:<\/strong><\/p>\n
SELECT * FROM DataFlair;\r\n<\/pre>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
In the above example, we can see a table with various records or tuples.<\/p>\n
2. RDBMS Tuple(A record)<\/h4>\n
In the database, we have data put in various tuples. These tuples are what we know as rows under the attributes. The tuple, row, and record terms are put interchangeably here.<\/p>\n
Example:<\/strong> Let us have a look at a single tuple in our DataFlair database.<\/p>\n
SELECT * FROM DataFlair \r\nLIMIT 1;\r\n<\/pre>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
Here we can see what a single tuple or row represents in a database.<\/p>\n
3. RDBMS Column(Attribute)<\/h4>\n
Attributes are commonly known as column names and are used to map data to the correct name. Column is\u00a0 a vertical entity in a table.<\/p>\n
Example:<\/strong> Let us have a look at the name column in our Dataflair database.<\/p>\n
SELECT name FROM DataFlair ;\r\n<\/pre>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
Here we can see what a column is in a database.<\/p>\n
We can also view multiple columns by specifying multiple column names in the query.<\/p>\n
4. RDBMS Domain<\/h4>\n
The domain of a database is the permissible values that a database can store.<\/p>\n
Example:<\/strong> When we talk about age, the age can\u2019t be negative thus, the domain is greater than 0. Let us view the same.<\/p>\n
SELECT age FROM DataFlair;\r\n<\/pre>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
Here we can see the age column in the DataFlair database and we can observe that the domain of the column is only positive values.<\/p>\n
5. RDBMS Schema<\/h4>\n
Schema is the composition of a table. In simple words, the columns and the type of data they store is the schema of the database.
\nExample:<\/strong> Let us view the schema of our DataFlair database.<\/p>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
Here we can see the composition or the schema of our DataFlair database.<\/p>\n
6. RDBMS Constraints<\/h4>\n
These are the rules which we want to impose on our data when it is put and maintained in our database.<\/p>\n
By the use of constraints, we maintain the integrity and accuracy of our data. We could have column level or table level constraints depending on our use case.<\/p>\n
Let us first understand the concept of NULL values and then we will discuss constraints further:<\/p>\n
RDBMS NULL values:<\/strong><\/p>\n
When some data is missing or not available at the moment, we use a placeholder for such data in the database.<\/p>\n
These placeholders are null values. We can reassign the null values at any time and prevent errors from creeping in due to the missing data.<\/p>\n
Example:<\/strong> Let us check if we have an employee with the location not available or null in our DataFlair database.<\/p>\n
SELECT * FROM DataFlair where location = null;\r\n<\/pre>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
Here we can see the details of an employee whose location is not specified i.e. NULL.<\/p>\n
Some of the major constraints we use are as follows:<\/p>\n\n\n\n\n\n\n\n\n\n\n
Sr.No<\/b><\/td>\nConstraint<\/b><\/td>\nDescription<\/b><\/td>\n<\/tr>\n
1<\/span><\/td>\nNOT NULL<\/span><\/td>\nPrevents the column from taking NULL values.<\/span><\/td>\n<\/tr>\n
2<\/span><\/td>\nDEFAULT<\/span><\/td>\nSets a default value for the column.<\/span><\/td>\n<\/tr>\n
3<\/span><\/td>\nUNIQUE<\/span><\/td>\nPrevents duplicate values in the column.<\/span><\/td>\n<\/tr>\n
4<\/span><\/td>\nPRIMARY KEY<\/span><\/td>\nHelps to identify each record uniquely.<\/span><\/td>\n<\/tr>\n
5<\/span><\/td>\nFOREIGN KEY<\/span><\/td>\nHelps to identify each record in another database uniquely.<\/span><\/td>\n<\/tr>\n
6<\/span><\/td>\nCHECK<\/span><\/td>\nApplies certain conditions on the column data.<\/span><\/td>\n<\/tr>\n
7<\/span><\/td>\nINDEX<\/span><\/td>\nHelps in creating and retrieving records fast.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Example:<\/strong> Let us view the Primary Key in our DataFlair database.<\/p>\n
Output:<\/strong><\/p>\n
\"RDBMS<\/a><\/p>\n
Here we can see in the columns that emp_id is the Primary key of our DataFlair database.<\/p>\n
Data Integrity<\/h3>\n
\"RDBMS<\/a><\/p>\n
The major categories of Data Integrity in an RDBMS are as follows:<\/p>\n
1. Entity Integrity:<\/strong> According to this principle, we can\u2019t have any duplicate tuples in a table.<\/p>\n
2. Domain Integrity:<\/strong> According to this principle, we make sure to store data in the correct format, type, and range in any column specified.<\/p>\n
3. Referential Integrity:<\/strong> According to this principle, we can\u2019t delete records that are required to access other records.<\/p>\n
4. User-Defined Integrity:<\/strong> According to this rule, the rules specified by the user while creating the database are always applied and checked before data is put in the database.<\/p>\n
NULL Value<\/h3>\n
Null values are used when we want to substitute the missing information.<\/p>\n
The null value is ignored by some SQL functions to work logically correctly. Null value comes in handy during analytics of large chunks of data which has missing or ambiguous data.<\/p>\n
Database Normalization<\/h3>\n
Database normalization is the process of filtering and organizing data in a database. We need to do normalization of a database for the following reasons:<\/p>\n