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Databases Modifying Data with SQL Adding Data to a Database Review and Practice

John Grillo
John Grillo
30,241 Points
Posted by John Grillo
John Grillo
30,241 Points

SQL, NULL's and auto-increment -- is typing 'null' necessary?

My question is straightforward. In the review, Chalkley says that using the NULL statement can trigger auto-incrementing columns. My question is, do you have to? Maybe it's different in SQLite, but I recall being able to just INSERT INTO the columns that didn't auto-increment, omitting the ID column in his example and it handles that automatically [since it inserts into the next row].

So do I have to write NULL into those insert statements, or will it auto-increment if I omit that column altogether?

5 Answers

jcorum
jcorum
71,830 Points

Yes, you can omit the id column from the field list and NULL from the values list. The editor accepted this:

INSERT INTO products (name, description, price) VALUES ("x", "y", 23)
John Grillo
John Grillo
30,241 Points
John Grillo
John Grillo
30,241 Points

yes, the editor accepted this and it's how i passed but i wanted to confirm that it was considred acceptable practice to do so.

Boban Talevski
Boban Talevski
24,793 Points
Boban Talevski
Boban Talevski
24,793 Points

Just to add that in case you don't specify the column names, then you need to enter NULL for the id column.

So while this passes ok

INSERT INTO actors (name) VALUES ("John Smith");

This doesn't

INSERT INTO actors VALUES ("John Smith");

and you would have to use NULL like this

INSERT INTO actors VALUES (NULL, "John Smith");
Vijeth Krishna
Vijeth Krishna
1,381 Points

Thanks for the great explanation

Tyler Brandt
Tyler Brandt
4,729 Points
Tyler Brandt
Tyler Brandt
4,729 Points

Hey John,

In an example on W3schools.com, they state that you do not have to specify a value for the "ID" column if it is auto-incrementing.

Code example from them below.

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');
fady mohamed
fady mohamed
5,972 Points

Hey Tyler, I know it's been a year, but thought i'd mention for anyone reading this. In that example the column names have been specified and that is why you can omit the ID column name and value as it would be taken as NULL. In the case that column names are not specified you must enter a value for all the columns and if no value is to be entered then NULL must be used. At least that is what I have come to understand.

David Corrales
David Corrales
4,698 Points
David Corrales
David Corrales
4,698 Points

For some reason this isn't working, would someone be able to find out why?

INSERT INTO movies (id, title, year_released, genre) VALUES (NULL, E.T. the Extra Terrestrial, 1982, Sci-Fi);

Daniel Phillips
Daniel Phillips
26,940 Points

I'm not sure if your quotes got stripped by the comment parser, but if you don't have quotes around your strings, that will cause a problem.

INSERT INTO movies (id, title, year_released, genre) VALUES (NULL, "E.T. the Extra Terrestrial", 1982, "Sci-Fi");
patrick wollner
patrick wollner
1,821 Points
patrick wollner
patrick wollner
1,821 Points

writing the id-value sure is optional yet usefull if you want to insert test data with high ids , or are manually fiddeling around with the values inside the database