Database - Introduction to SQL - Discussion

You are right, agree @Ahmed.

Can anyone please explain why option (D)?

Because we make one table for particular department or employee we use datatype otherwise compiler cannot identify which type of data insert in table.

Can anyone please explain to me why option (D) All of the above, why not option (A) Datatypes?

Making full table, all are valuable.

What is meant by default value in SQL?

I too agree with you @Dev.

I agree with you @Dev.

Primary key and default values are optional. For creating table we need to consider the data type.

But if we don't use primary keys and default values then also there is no problem in table creation. But data types must be provided prior.

Because if there null values. When calculating the column values.

If there is null then the total will be '0'.

(anything + null = 0).

If we use default value '0' at integer column.

If we not specified the value then the 0 will be inserted in that column.

Then the total result will be correct. And also for char column it changes default. That if we don't know a person name. Instead of leaving it null. If we put default as 'not specified' then 'not specified' will be inserted in column. And so on.