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0 pointsgiornogiovanna6y ago0 comments

1. NOT NULL is very frequently used in schemas, because NULL is often an undesirable value (e.g. for a mandatory field). That doesn't make NULLs bad, and NULLs are still frequently used when you have optional fields or fields where NULL has some other special meaning.

2. NULLs are used by SQL functions and operators as an "unknown" value. So, for example, "NULL AND TRUE" is NULL, because we could substitute NULL with TRUE or with FALSE to get different results, but "NULL AND FALSE" is FALSE, because no matter what we substitute NULL with, the result will always be FALSE.

3. Clearly all these valid uses of NULL do not indicate "flaws" in the database design.

4. Database normalization isn't always a good thing, and beyond a certain level it's almost always a bad thing, so using normalization methods as a standard for whether something is "flawed" is probablyn ot the best idea.

5. No database normalization method, as far as I know, actually tries to eliminate NULLs, so I don't know what "(See database normalizations)" refers to. Can you clarify?

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tabtab6y ago

Re: NOT NULL is very frequently used in schemas, because NULL is often an undesirable value

Talking strings, usually if you don't want a null string, you also don't want blanks (white space) either. I'd like to see auto-trim in the standard, and also a minimum length specifier. We then wouldn't need to deal with nulls. A single min-length-when-trimmed-and-denulled integer value would replace a lot of repetitious hubbub in typical CRUD apps. D.R.Y. it! You'd have one attribute "cell" that would replace the equivalent of:

     IF length(trim(denull(inputValue,''))) 
        < this_fields_min_length THEN
         raise_data_too_short_error(...);

That's the way you'd want it done in the vast vast majority of CRUD systems (if not doing weird things).

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