What is the null value Problem in DBMS?

Hello Friends, In this blog post we are going to let you know about ‘What is the null value Problem in DBMS’. A null is used to represent the unknown and missing values. However, it does not mean that the null value is equivalent to zero or a blank text string. See the example below for the same.

Inside this blog(What is the null value Problem in DBMS) we are going to cover What is the meaning of null value? How are null values caused? What is allowed null in the database? What is the null value in DBMS? What is a null attribute in DBMS?

Table: Client

Client ID	First Name	Middle Initial	Last Name	City	Country
1	John	B	corner	Allenspark	Null
2	Mary	Null	levis	Wiseland	East Midlands
3	Timmy	J	Finco	Poolshire	Mersybindo
4	Halk	Null	Jamur	Sillyvelly	Null
5	Yen	Null	hui	Newcity	North Brazil
6	Nayan	K	Bansal	Mumbai	India

How null values are created or inserted into the database?|What is the null value Problem in DBMS?

It is good to have null values in the table whenever they are just for showing purposes like a Middle name or stating some information.

As you can see in the above client table null is useful to show the middle initial field and the country field. If we want to use this null properly then we should know the reason for their occurrence.

The very first reason for null values could be a manmade error. While entering the data in the table, we forget to ask a particular client say John which country he lives in.

Thus this missing data will be shown including a null value. You can see the country column for John in the above table.

There could be lots of reasons to fill a field with the value null. The value that has not been defined for that field could be one of the reasons.

Let’s understand this scenario with an example related to the above table.

Assume that we asked John about the country information he is living in but unfortunately, he does not know his country name and you also don’t have any idea about his country then we have to set a null value in his country column.

There could be another case where we need to insert the null value for a field.

For example, in a company, an employee is working both day and night shifts, there are the field total hours worked for the day and night shifts both.

Assume that he is on the night shift for one month then his total hours worked on the day shift will be always null for one month. So, in this case, the null value comes as per the condition.

Problems with null: What is the null value Problem in DBMS

In general null value does not impact anything until it is used just for showing the status of any field. But once that field is used in mathematical calculation with some other logical field then it can impact the outcome result.

(50 x 3) + 10 = 160
(Null x 4) + 25 = Null
(20 x Null) + 500 = Null

With the help of below product table below, you can see the impact of the null value on a mathematical calculation.

Table: Product

Product Code	Product Name	Product Category	Price	stock	StockValue
1	Fight with Truth	Books	Null	10	Null
2	Fight with Truth	Books	30.95	5	154.75
3	28 LED	Null	120	Null	Null
4	HP Printer Ink Tank	Null	70	10	700.00
5	Videocon LCD with home theater	Audio/Visual	90	Null	Null
6	Hard Disc 1Tb	Device	55	15	825.00

You can easily understand the problems due to the null value by inspecting the value of the above product table. Here stock value is derived by the multiplication of price and stock field like[Price*stock]. So, for product 1 where the price is null, the stock value will always show null.

This problem can be more critical when you need to calculate the total value of all the items which are kept current in stock then you can not get an accurate result for the same.

to address this problem you need to make sure that the price and stock fields can’t be assigned as null.

See another example where a null value is affecting an aggregate function.

Null values will also affect the aggregate function that incorporates the value of a given field. If we were using an aggregate function, for example, a count function, the result will always contain a null if the field contains a null.

The table below shows the results of performing a summary calculation that will count the number of occurrences of a category in the products table.

Let’s take an aggregate function which is counting the Product category column.

Category calculus

category description	Total no. of Occurrences
	0
Audio/Visual	1
Books	2
Device	1

After applying the aggregate function we can see the effect of the null value.

Count ProductCategory:

Here is the result of category calculus, we can observe that the occurrence of the unspecified category is 0, whereas if we see the product table then we can easily find that two products do not show any category.

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Conclusion:

So, in this blog(What is the null value Problem in DBMS), you have learned how the null value is inserted into the database table. It can be entered by human mistake and sometimes data is unknown at present and we leave that field and by default, it is filled with null. And some time information does not match a particular column and is thus filled with null. You have also read about the effect of these null values in mathematical operations and aggregate functions.

Within this blog post(What is the null value Problem in DBMS), we have gone through What is the meaning of null value? How are null values caused? What is allowed null in the database? What is the null value in DBMS? What is the null attribute in DBMS? NULL values in DBMS ppt Disadvantages of NULL values in the database, the NULL value in DBMS in Hindi, What is a null, NULL attribute in DBMS, Inserting NULL values in SQL, Comparison using NULL values, Importance of NULL values in a relational database.

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