Database - First Normal Form (1NF)

First Rule of 1NF

You must define the data items. This means looking at the data to be stored, organizing the data into columns, defining what type of data each column contains and then finally putting the related columns into their own table.

For example, you put all the columns relating to locations of meetings in the Location table, those relating to members in the MemberDetails table and so on.

Second Rule of 1NF

The next step is ensuring that there are no repeating groups of data. Consider we have the following table −

CREATE TABLE CUSTOMERS(
   ID   INT              NOT NULL,
   NAME VARCHAR (20)     NOT NULL,
   AGE  INT              NOT NULL,
   ADDRESS  CHAR (25),
   ORDERS   VARCHAR(155)
);

So, if we populate this table for a single customer having multiple orders, then it would be something as shown below −

ID	NAME	AGE	ADDRESS	ORDERS
100	Sachin	36	Lower West Side	Cannon XL-200
100	Sachin	36	Lower West Side	Battery XL-200
100	Sachin	36	Lower West Side	Tripod Large

But as per the 1NF, we need to ensure that there are no repeating groups of data. So, let us break the above table into two parts and then join them using a key as shown in the following program −

CUSTOMERS table −

CREATE TABLE CUSTOMERS(
   ID   INT              NOT NULL,
   NAME VARCHAR (20)     NOT NULL,
   AGE  INT              NOT NULL,
   ADDRESS  CHAR (25),
   PRIMARY KEY (ID)
);

This table would have the following record −

ID	NAME	AGE	ADDRESS
100	Sachin	36	Lower West Side

ORDERS table −

CREATE TABLE ORDERS(
   ID   INT              NOT NULL,
   CUSTOMER_ID INT       NOT NULL,
   ORDERS   VARCHAR(155),
   PRIMARY KEY (ID)
);

This table would have the following records −

ID	CUSTOMER_ID	ORDERS
10	100	Cannon XL-200
11	100	Battery XL-200
12	100	Tripod Large

Third Rule of 1NF

The final rule of the first normal form, create a primary key for each table which we have already created.

sql-rdbms-concepts.htm