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In MySQL or any programming language, there are privileges to add constraints or checks in the instance of creating a table. These constraints help the user to restrict the values ​​inserted into specific fields of the table.

The restriction allows the user to enter a well-defined set of data in the column. However, if these constraints are not applied at schema creation time, you can choose to extract rows by applying a query.

Check if a column is Null or Empty in MySQL

The steps to filter out null or empty column values ​​present in the table are given in the previous section.

The syntax for NULL or Empty check is:

Select expression [, expression2] ...
     FROM table-name
    [WHERE column-name IS NULL or column-name = '']

In the above query, the basic syntax of Select is used to form a statement to extract null and empty values ​​from the table. Specifically, some keywords like IS NULL are used with the column name to filter out the null values.

Whereas for null check, simple match of column name with blank characters is checked. This combination of IS NULL keyword in Select query extracts subset rows that have null or empty value in column name.

Let's look at the IS NULL check in detail:

IS NULL keyword is an operator which is used to check the null value of a column. It is an intermediate operator which is used with other queries to perform operations like select, update, and delete in MySQL.

List of queries before actually checking the query on the table:

1. Create a table using the create query in MySQL. The query will create the initial schema.

   Create table student ( id varchar(255), name varchar(255), dob date);
   

   In the above query, no constraints such as primary key, uniqueness, or not null are used. Therefore, the pattern extracts the desired results.

   Adding a screenshot of the created table for reference.

   

2. Insert some values ​​into the table.

   Insert into student values ( null,'Josheph', '2022-06-08');
   Insert into student values ( '117','', '2022-06-06');
   

   The above query inserts some required values ​​into the table. Other values ​​can be added as well.

   Below are screenshots for reference.

   

3. Rows actual query to filter empty and null rows.

   Query and execute MySQL statements:

   Select * from student where name IS NULL or name = '';
   Select * from student where id IS NULL or id = '';
   

   The above query extracts the list of values ​​from the above table whose names are null or empty. Similarly, in the second Select query, the check on the ID field property matches the empty character value or the null value.

   Below is a screenshot of the actual local operation for reference.

   Local running screenshots: