Skip to content

SQL, Handling empty cells

New Course Coming Soon:

Get Really Good at Git

How to handle null data in a SQL database

When we create a table in this way:

  age INT,
  name CHAR(20)

SQL freely accepts empty values as records:

INSERT INTO people VALUES (null, null);

This might be a problem, because now we have a row with null values:

 age |  name  
  37 | Flavio
   8 | Roger

To solve this, we can declare constrains on our table rows. NOT NULL prevents null values:

  name CHAR(20) NOT NULL

If we try to execute this query again:

INSERT INTO people VALUES (null, null);

We’d get an error, like this:

ERROR:  null value in column "age" violates not-null constraint
DETAIL:  Failing row contains (null, null).

Note that an empty string is a valid non-null value.

Are you intimidated by Git? Can’t figure out merge vs rebase? Are you afraid of screwing up something any time you have to do something in Git? Do you rely on ChatGPT or random people’s answer on StackOverflow to fix your problems? Your coworkers are tired of explaining Git to you all the time? Git is something we all need to use, but few of us really master it. I created this course to improve your Git (and GitHub) knowledge at a radical level. A course that helps you feel less frustrated with Git. Launching May 21, 2024. Join the waiting list!
→ Read my SQL Tutorial on The Valley of Code

Here is how can I help you: