[Year 12 IT Apps] ITA U3O2 key knowledge 9

[Mike Brookes]

In microsoftspeak date/time is a single data type. Date/times are stored 
as a decimal value giving the days from jan 1 1900
the bit after the decimal point is then formatted in hours/min/sec or 
whatever you wish.
ie date/times are stored as a single floating point number which is then 
formatted as date and/or time - this is much more efficient than storing 
as text

Mike Brookes
Chief cook and bottle washer Copperfield College

On 12/04/2010 2:07 PM, Mark KELLY wrote:
> Hi all.  Welcome back to work.
>
> 1.  Need a bit of help reading a database KK dotpoint - "data formats, 
> including limited length, unlimited length, *incremental* (text); 
> integer, auto string number, long (number); date, 24-hour clock 
> (date/time); dollar (currency); true and false (representation of 
> Boolean logic)"
>
> I have not come across 'incremental' text fields before.  Googling 
> suggests it might perhaps be referring to the auto-entry of 
> incrementing serial numbers into a field?
>
> And later it refers to 'auto string number' - is this an auto-entered 
> numeric serial number?  In which case, what does 'auto *string* 
> number' mean?
>
> N.B. the term '*incremental' *did not appear in the draft study 
> design.  Also, the mysterious 'auto string number' did not appear: 
> instead there was the clearer 'auto incremented number'... is that 
> what the accredited SD meant to say?
>
> Any suggestions, anyone?
>
> --------------
>
> 2. While I'm on this KK, I'm wondering about the usage of the term 
> 'data format'.  I've believed data format refers to the way data is 
> *presented* (e.g. a date could be shown as text or in a calendar 
> control; numbers can be formatted with different number of decimal 
> places, thousands separators, right justified etc).
>
> But KK9 refers to things like integer and long as being data formats 
> rather than data types, which I'd call them since they define the 
> storage needs of the data rather the way it is formatted in output.  
> Much the same applies to limited & unlimited length text fields: they 
> do not differ in appearance, they are fundamentally different types of 
> storage entities.
>
> And date and time are listed as formats of date/time.  Again, I would 
> argue that they are distinctly different field types rather than 
> display variants.  In Filemaker, my primary RDBMS tool, there are 
> different field types for date, time and timestamp (a combination of 
> date and time in one container). Of course dates and times can be 
> formatted in various ways in output, but they are not stored the same...
>
> I am happy with the other data formats mentioned in KK9 such as 
> currency being a special format for numbers, but in the previous 
> dotpoint currency is also mandated as a data *type*.  This may be 
> because Access confuses things by having both a currency *format* and 
> a currency *datatype*) - I'm looking at looking at 
> http://www.everythingaccess.com/tutorials.asp?ID=Using-the-Currency-field-data-type---without-the-hassle. 
> Filemaker does not have a currency data type... do other RDBMS?  I 
> hope this is not another case of Access parochialism.
>
> I think we need to be rather careful distinguishing between field 
> *types* (U3O2KK8) and field *formats* (U3O2KK9).
>
>
> -- 
> Mark Kelly
> Manager - Information Systems
> McKinnon Secondary College
> McKinnon Rd McKinnon 3204, Victoria, Australia
> Direct line / Voicemail: 8520 9085
> School Phone +613 8520 9000
> School Fax +613 9578 9253
> kel at mckinnonsc.vic.edu.au <mailto:kel at mckinnonsc.vic.edu.au>
>
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