MySQL Check if Column is Null

MySQL Check if Column is Null

Introduction

There are several reasons why you might want to check if a column is NULL in MySQL:

  • To filter query results - You might want to exclude rows with NULL values from your query results. For example, you might want to get a list of all users who have provided their email addresses but exclude those who have not.

  • To update or delete rows - You might want to update or delete only those rows that have NULL values in a particular column. For example, you might want to set a placeholder value for all users who have not provided one.

  • To handle missing data - In many cases, NULL values can indicate erroneously missing or unknown data. Checking for NULL values can help you handle this data appropriately in your application.

  • To enforce data integrity - You might want to ensure that certain columns are not NULL in order to maintain integrity of your data. For example, you might want to ensure that all users have a non-NULL email address.

Overall, checking for NULL values can be an important part of working with data in MySQL.

In this short article, we'll take a look at what NULL in MySQL is and how to check if a column is NULL. Additionally, we'll go over an example query that finds both NULL and empty fields in the specified column.

What is NULL in MySQL

In MySQL, NULL is a special value that represents the absence of a value. It is not the same as an empty string or the number 0, for example.

A column in a MySQL table can be defined as NULL, which means that it can store NULL values. This is different from a column that is defined as NOT NULL, which means that it cannot store NULL values and must be given a value when a new row is inserted into the table, lest an error be raised.

How to Check If a Column is NULL in MySQL

Now, we can hop on the actual query that will filter out all NULL values from the example column. To check if a column is NULL in MySQL, you can use the IS NULL operator:

SELECT * FROM table_name WHERE column_name IS NULL;

This will return all rows from table_name where the value in column_name is NULL.

You can also use the IS NOT NULL operator to check for non-NULL values:

SELECT * FROM table_name WHERE column_name IS NOT NULL;

This will return all rows from table_name where the value in column_name is not NULL.

Note: Keep in mind that NULL is a special value in MySQL that represents the absence of a value. It is not the same as an empty string or the number 0.

Aditionally, we can take care of all special values that might represent absence of the column entry (NULL, 0, and empty string) in a single query:

SELECT * FROM table_name WHERE column_name IS NULL OR column_name = '' OR column_name=0;

This will filter all rows from table_name where the value in column_name is one of the following: NULL, 0 or an empty string.

Conclusion

In conclusion, checking if a column is null in MySQL can be done using the IS NULL operator in a SELECT statement. This operator can be used in a WHERE clause to filter the result set and return only rows where the specified column is NULL.

It is also possible to use the IS NOT NULL operator to return rows where the column is not NULL. It is important to note that NULL values represent missing or unknown data, and they are different from zero or an empty string. By using the IS NULL and IS NOT NULL operators, you can effectively handle NULL values in your MySQL queries and ensure that your results are accurate and meaningful.

Last Updated: December 30th, 2022
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