The document discusses shortcomings of how most databases store date-time data. It notes that date-time is typically stored as a single column containing multiple values like month, day, and year, violating the rule of guaranteed access. This makes it difficult to retrieve results for just the date portion without the time. Date-time also cannot store additional details like day of the week or support dates beyond 9999. The document proposes an alternative model and provides scripts and images demonstrating issues with the current approach.

1. It’s not just another article on Date-Time, But, RDBMS VIOLATIONS BY So-Called RDBMS Products!!!
Praveen Kumar Peddi
Objective:
The document intends to cover the short comings of existing data storage of date time data type and provides a
solution to them in truly relational data model and benefits of the model and most benefited areas of the systems.
Current data storage model for Date-time datatype:
At Present, Data storage of “date-time” includes both date and time as well in a single column. Almost across all
database products, storage and data retrieval of “date-time” data type is implemented as given in the below Table:
Product Data Type Description
SQL Server Datetime Date and Time Values from January 1, 1753, through
December, 31, 9999 accurate to 3 milliseconds
SQL Server Smalldatetime Date and Time Values from January 1, 1900 through
June 6, 2079, accurate to one minute.
Oracle Date Oracle Format that includes not just the Month, day,
And year , but also the hour , minute and second.
Oracle TimeStamp TimeStamp data type Stores the date to the billionth of a
Second.
DB2 Date stores a date value (month, day, and year) in Proprietary
character data types in internal format and its
external format is MM-DD-YYYY or MM/DD/YYYY
DB2 Time stores the time value (hour, minute, and second) in
Proprietary character data types in internal format and
Its external format is HH.MM.SS or HH:MM:SS
DB2 TimeStamp Type combines the date and time but stores the time
Down to the nanosecond. Its External Format is MM-
DD-YYYY-HH.MM.SS.NNNNNN
Summary:
Put Together, Almost All Products includes [month, day, and year] in their respective Primary “date”
data types.
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2. Short-Comings of Current data storage model for Date-time datatype:
a) Date-t ime Stores the mult ip le values in single column, (month,
day and year at least) , which means date-t ime data type is not
atomic
b) I t
Primari l y vio lates the Codd’s Rule Of Guaranteed Access:
What is Codd’s Rule of Guaranteed Access i t?
Each and Every Datum (atomic value) in a relat ional database is
guaranteed to be logical l y accessible by resort ing to a combination
of table name, primary key value, and column name.
c) Unless t ime part is expl ic i t l y
specif ied, i t wil l only return
the results for the exact matching of “date” values.
Date t ime does not store day of the week, as part of i t .
d)
EX: October, 7th 2009, does not specify , whether i t is Sunday or
Monday.
E) Date t ime data-type does not have the capabil i t y to store and
display the data for dates beyond 9999-Dec-31.
F) In addit ion, we need to re-cal l the rule of thumb that date
t ime
column cannot be used a primary key or Unique key.
[Those who want to dir t their hands on their own, can move to current
model scripts, cut/copy, paste and run!] .
[Those who are not techies, but interested to have a look and feel ,
may see the images for outcome of demonstrat ions].
Scripts:
datetime_currentmo DateTime_ShortComi DateTime_ShortComi DateTime_ShortComi
del.sql ngs_001.sql ngs_002.sql ngs_004.sql
DateTime_ShortComi
ngs_005.sql
Images:
datetime_currenntm datetime_short_comi datetime_short_comi datetime_short_comi datetime_short_comi
odel.jpg ngs_001.jpg ngs_002.jpg ngs_004.jpg ngs_005.jpg
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3. Yes! Feedback is appreciated.
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