I seem to remember that (on Oracle) there is a difference between uttering select count(*) from any_table and select count(any_non_null_column) from any_table. What are the differences between these ...
Think of x as a column containing null, 0, 1. Only less than 1 % of the rows contain 1. There is no logical difference between 0 and Null. Is it a good idea to insist, that isnull rather than NVL is ...
In MySQL, is it better to always allow nulls unless you know a field is required, or always use Not Null unless you know a field will contain nulls? Or doesn't it matter? I know in some DBMSs they ...
I'm interested mainly in MySQL and PostgreSQL, but you could answer the following in general: Is there a logical scenario in which it would be useful to distinguish an empty string from NULL? What ...