Would anyone ever recommend storing dates and numbers in the same field? [closed]_问答_开发者

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As background, I'm one of two developers in my department. I got into computers my freshman year in high school (1986) and have no formal education. I got into MS Access a little bit in 1994 and more seriously beginning in 2003. I'm self-educated, have always tried to learn as much as I can about database design, and while I believe I know a lot I also know I don't know everything.

The other developer in my department, according to his resume, has a degree in computer science and has been doing IT work, including web design and database design, for about 8 years. He was hired into my department last December. I've been very surprised by what I see as a very fundamental lack of knowledge about the basics of database design and SQL and have been trying to figure out if at least part of the problem is I'm expecting too much or maybe don't know as much as I think I do.

Hence my question. Please note we are 100% MS Access, but I believe this question applies to about any SQL database. This developer was tasked to take a spreadsheet and convert it into a database. Part of the spreadsheet involved tracking inventory for batteries. In the spreadsheet, the column titles were Date and Count. But the data in the date column was a mix of dates and batch numbers. So this developer created a table with a nume开发者_StackOverflow社区ric field to contain both the batch number and the date and a second boolean field called IsDate to indicate what value was in the field.

I disagree with this approach and would have created two separate fields, a date field for the date and a numeric field for the batch number. When I suggested this approach, he seemed to not only not understand why but also to get a bit angry about having to change his design.

Which approach would you recommend? Also, assuming everyone agrees with my approach - of course you will! ;) - if you had a developer with this supposed level of experience, would you consider him worth keeping and worth investing the time and effort to educate him?

My own rule of thumb here is:

Always keep data in a native datatype.

This helps comparing, sorting, finding and grouping - especially in a database - and makes your storage less prone to query errors. Moreover, you're not required to use another predicate (AND isdate) when accessing the data. Hence, I think your approach is correct.

Your colleague's approach seems not to be a matter of high education, but one of a personal approach. I've seen workers with PhD who could well listen to a well-reasoned argument, and freshmen who made grave mistakes and would not listen to a polite advice.

I'd most definitely store the date and the batch number in different fields of the appropriate type - setting each with the relevant content or as NULL if no value was available. By doing this you'd be able to see what data you actually have available and perform meaningful operations on that data.

In terms of you second question, I guess it would really depend on what the developer in question said when you asked them why they'd chosen the approach they did.

You are right.

Only under severe memory restrictions might (note might) this kind of architecture be acceptable.

As to dealing with him, I would first talk to him and fiugre out why he chose the given approach, this is something that might have been common in Access Databases 10 years ago (but even then there was enough disk and memory space to not have to do these kind of tricks).

His reluctance to talk about his design is a worse indicator of his abilities than the design itself. Even the most misguided design should have been based on a structured approach or idea. In my mind it is not a bad thing to be wrong, it is a bad thing to create random structures. But not knowing your requirements it is hard to suggest whether it is worth keeping him or not.

Is one of you the 'senior' hierarchy wise or are you sharing responsibilities ?

Point out that he is breaking first normal form by doing so. Be able to describe 1NF 2NF and 3NF before trying to impress him with you fancy pants knowledge.