Introduction
There are a number of explanation why you may need to test if a column is NULL in MySQL:
-
To filter question outcomes – You may need to exclude rows with
NULLvalues out of your question outcomes. For instance, you may need to get a listing of all customers who’ve offered their electronic mail addresses however exclude those that haven’t. -
To replace or delete rows – You may need to replace or delete solely these rows which have
NULLvalues in a specific column. For instance, you may need to set a placeholder worth for all customers who haven’t offered one. -
To deal with lacking knowledge – In lots of circumstances,
NULLvalues can point out erroneously lacking or unknown knowledge. Checking forNULLvalues will help you deal with this knowledge appropriately in your software. -
To implement knowledge integrity – You may need to be certain that sure columns are usually not
NULLso as to preserve integrity of your knowledge. For instance, you may need to be certain that all customers have a non-NULLelectronic mail handle.
Total, checking for NULL values might be an essential a part of working with knowledge in MySQL.
On this brief article, we’ll check out what
NULLin MySQL is and the right way to test if a column isNULL. Moreover, we’ll go over an instance question that finds eachNULLand empty fields within the specified column.
What’s NULL in MySQL
In MySQL, NULL is a particular worth that represents the absence of a worth. It’s not the identical as an empty string or the quantity 0, for instance.
A column in a MySQL desk might be outlined as NULL, which implies that it may well retailer NULL values. That is completely different from a column that’s outlined as NOT NULL, which implies that it can not retailer NULL values and have to be given a worth when a brand new row is inserted into the desk, lest an error be raised.
Tips on how to Test If a Column is NULL in MySQL
Now, we are able to hop on the precise question that may filter out all NULL values from the instance column. To test if a column is NULL in MySQL, you should use the IS NULL operator:
SELECT * FROM table_name WHERE column_name IS NULL;
It will return all rows from table_name the place the worth in column_name is NULL.
You too can use the IS NOT NULL operator to test for non-NULL values:
SELECT * FROM table_name WHERE column_name IS NOT NULL;
It will return all rows from table_name the place the worth in column_name just isn’t NULL.
Observe: Understand that NULL is a particular worth in MySQL that represents the absence of a worth. It’s not the identical as an empty string or the quantity 0.
Aditionally, we are able to maintain all particular values that may signify absence of the column entry (NULL, 0, and empty string) in a single question:
SELECT * FROM table_name WHERE column_name IS NULL OR column_name = '' OR column_name=0;
It will filter all rows from table_name the place the worth in column_name is among the following: NULL, 0 or an empty string.
Conclusion
In conclusion, checking if a column is null in MySQL might be carried out utilizing the IS NULL operator in a SELECT assertion. This operator can be utilized in a WHERE clause to filter the consequence set and return solely rows the place the required column is NULL.
Additionally it is potential to make use of the IS NOT NULL operator to return rows the place the column just isn’t NULL. You will need to observe that NULL values signify lacking or unknown knowledge, and they’re completely different from zero or an empty string. By utilizing the IS NULL and IS NOT NULL operators, you’ll be able to successfully deal with NULL values in your MySQL queries and be certain that your outcomes are correct and significant.
