Let us try to clean up your code and help you build good habits since you are new to this. First of all, a table must have a key and models a set of entities.
But a key cannot be NULL by definition! All your columns can be NULL, so you can never have a key and therefore it will never be a table. Now let's go line by line.
The use of the absurd "tbl-" affix is so bad it has the nickname "tibble" and there's even a little poem about it. Also, do you really have only one student? That's what you said!
Calling a column "id" is useless. It needs to be student_id (you can read the metadata committee standards or ISO11179 for the rules). But if it is an identifier, and that has to be measured on a nominal scale (have you had a class on the types of scales and measures?) Values on nominal scale have to be character data, since they are not qualities or magnitudes.
Likewise, the second column has to be the name of something in particular. I will guess it is the student's name. Do you really have students whose names are 100 characters long? If you leave the space for it. You'll get at least one or two of them! I like to use 30 or 35 characters because that's what the international Postal Service uses on address labels. There are also standards for the street address, postal codes and country. But you seem to want to squeeze it all into one line and not break it down to fields; okaygo ahead and stick with that, but it's a bad design.
Why are you using floating points for marks? This is why we have DECIMAL(s,p) datatypes. I seriously doubt if you've had the two weeks we needed from. I wrote FORTRAN to learn how to handle floating-point math.
You could put some kind of comments in this table, but I just don't like doing that. SQL was never meant to handle text and comments often lead to little problems with the law. If you need comments secure them in the other table that references the students. Here is revised DDL
CREATE TABLE Students
(student_id CHAR(10) NOT NULL PRIMARY KEY,
student_name CHAR (30) NOT NULL,
student_address VARCHAR (100) NOT NULL,
student_mark DECIMAL (5,2) NOT NULL
CHECK(student_mark >= 0.00));
INSERT INTO Students
VALUES ('1000000001', 'Frank Imon', 'Ninth ring of hell ', 90.00);
Now the column count and data types match the parameters.
Please post DDL and follow ANSI/ISO standards when asking for help.