So I have a field called an Obsolete change date in a DB2 table which stores the date when a record was marked as Obsolete. I'm not able to figure out how to define this in the create table statement.
If i give default not null, it will enter a default value which is the current date which i dont want to be populated because if it got populated, it would indicate the record was made obsolete on the current date.
Also, I dont want to populate with NULL. So how can i handle this situation?
It appears that you are using a date field, so you could use the first valid date in the format date range as a default. In some places IBM treats 0001-01-01 as a null date, but that only works for formats with 4 digit years. For various date formats that would be:
FORMAT START END
4 digit years (e.g. *ISO) 0001-01-01 9999-12-31
3 digit years (e.g. *CYMD) 1900-01-01 2899-12-31
2 digit years (e.g. *YMD) 1940-01-01 2039-12-31
Date fields can only hold a valid date or null
Related
I'm working on tables obtained from a PervasiveSQL database and I have some trouble managing dates.
In some of the fields dates are recorded in the format we use in Italy, dd/mm/yyyy, but in others are recorded in a format I can't understand, something like this:
Start_Date 132384788
Last_Tx_Date 132385052
Last_Tx_Time 252711936
What kind of format is it?
How can I convert it in a human readable one?
I think that Start_Date could be August 8 2020 but I'm not sure.
Thanks for any help!
I tried to copy and paste tables in an Excel file but automatic dates conversion did not work.
The Start_Date and Last_Tx_Date fields look to be Btrieve Date fields. If you set the data type for that field in the DDFs to Date, it should show a human readable field. However the Last_Tx_Time field is a Btrieve Time (not timestamp) type.
From the Actian Zen v15.10 documentation (https://docs.actian.com/zen/v15/#page/sqlref/sqldtype.htm#ww136646):
Date:
The DATE key type is stored internally as a 4-byte value. The day and the month are each stored in 1-byte binary format. The year is a 2-byte binary number that represents the entire year value. The MicroKernel places the day into the first byte, the month into the second byte, and the year into a two-byte word following the month.
An example of C structure used for date fields would be:
TYPE dateField {
char day;
char month;
integer year;
}
The year portion of a date field is expected to be set to the integer representation of the entire year. For example, 2,001 for the year 2001.
Time:
The TIME key type is stored internally as a 4-byte value. Hundredths of a second, second, minute, and hour values are each stored in 1-byte binary format. The MicroKernel places the hundredths of a second value in the first byte, followed respectively by the second, minute, and hour values. The data format is hh:mm:ss.nn. Supported values range from 00:00:00.00 to 23:59:59.99.
I have a table with a column called that contains text. Most of the values are years. However, some have the value "present" to represent groups that are still currently active. I want to convert those values to today's year, and convert the column type to date (specifically year type). I want to avoid creating a new column if possible.
Please see below for the DAX language that worked.
= Table.ReplaceValue(#"Extracted Year2",null,DateTime.LocalNow() ,Replacer.ReplaceValue,{"Disbanded"})
There are probably many questions that are asking about date formats, but I haven't found anything like this.
I have a table, called t_birthday. t_birthday has a field called "DayOfMonth" which currently stores the data in a dd/mm/yyyy format. Lets say the record I have has the Date of 01/12/2016 (Dec 1, 2016).
Now, if I create a query using the "Query Design" option in the Create tab, I select my table t_birthday. For the field option, I select DayOfMonth. In the criteria option, I put =#01/12/2016#. When I click Run, it queries the database and returns the record with that date successfully.
However.. If I check the SQL generated from this Query Design, it is this:
SELECT t_birthday.DayOfMonth
FROM t_birthday
WHERE (((t_birthday.DayOfMonth)=#12/1/2016#));
If I try copy and pasting the DayOfMonth value from the table into that query, it wouldn't work. Notice how the format in the query is mm/dd/yyyy, but in my table it's still dd/mm/yyyy. I never touched any of the date formatting options in my table, or even on my computer. When I actually create this record using a form, I have a date picker which is in the form of dd/mm/yyyy as well.
Questions:
In the query design, when I specify criteria in dd/mm/yyyy, why does it generate sql in the form of mm/dd/yyyy?
I can only query dates using dd/mm/yyyy format if the day number (1-31) is 13 or above, OR if the month value and the day value are the same (October 17, Jan 1, March 3, November 11, December 12, etc). mm/dd/yyyy still works for those dates previously mentioned. I can't query dates like November 7th, Feb 3rd, August 4th, etc using dd/mm/yyyy though. How do I get around this problem? I store the dates, and I use the values directly from the table as conditionals in my queries. I shouldn't have to alter my date value in order to use them.
Why can I write an SQL statement for dates with the day number above 13 in dd/mm/yyyy format or mm/dd/yyyy format? E.g., the WHERE clause can look like: WHERE DayOfMonth=#13/06/2018 or WHERE DayOfMonth=#06/13/2018 and it still returns the same record? Why does access not enforce a specific format?
EDIT:
Currently I run my query in VBA and return it into a recordset using the following:
Dim bdayRecords As RecordSet
Dim sql As String
sql = "SELECT t_birthday.DayOfMonth"
sql = sql & " FROM t_birthday"
sql = sql & " WHERE (((t_birthday.DayOfMonth)=#" & rs("DayOfMonth") & "#));"
bdayRecords = CurrentDb.OpenRecordset(sql)
Where rs in the where clause was a previous recordset with a date value stored in "DayOfMonth". The rs recordset retrieved the date value from a different table in the exact same way bdayRecords was populated.
bdayRecords won't find the records with the date values matching the criteria explained before.
Use a properly formatted string expression for the date value retrieved:
sql = sql & " WHERE t_birthday.DayOfMonth = #" & Format(rs("DayOfMonth").Value, "yyyy\/mm\/dd") & "#;"
The ISO sequence yyyy-mm-dd works everywhere, so make it a habit to use that.
SQL always uses mm/dd/yyyy. That's not dependent on how you format it.
You never actually store a date in a certain format. You display a date in a certain format. All dates in Access are stored as a double-precision floating number containing the number of days elapsed since 30-12-1899, with fractions as time. How dates are formatted has no influence whatsoever on your SQL statement
Always use either mm/dd/yyyy or yyyy-mm-dd in your SQL. VBA only takes mm/dd/yyyy.
However, Access is opportunistic when working with clearly invalid dates, such as 13/1/2018. Because no 13th month exists, it parses it as the 13th of january, even though it's not a valid date.
If you're using values from other queries, there shouldn't be any problems, since the values never get cast back and forth to strings. You only get in trouble when casting a date to a string and then back to a date, which is not something you should do in queries, ever.
To avoid casting back and forth between strings, you can either refactor your code to a single query instead of retrieving a value from a recordset and inserting that value in a string SQL statement, or use parameters, which allows you to use the date value directly in an SQL statement.
For explanations why these design choices are made, ask Microsoft, they wrote the program. This is just how it works.
I have some FileMaker timestamp which I don't know how to handle. (I discovered it by trial...)
Does someone know an algorithm to convert FM (File Maker) timestamp into DateTime?
I have read about the format on this page. Which includes a "FM dec Timestamp" button which makes the desired conversion, but gives no reference on how it does so!
Also, my timestamps differs in format from the one required in the site, mine has a size of 18 digits, whearas the site only allows 11.
Inserting 634890864000000000 and removing the trailing zeroes (to leave 11 digits), I got this date:
Wednesday, 2012-11-21 10:20:00
If you have FileMaker this should be as simple as:
Importing the number as text,
Making a new calculation field, resultingTimestamp, which takes the left 11 characters and converts to a TimeStamp:
GetAsTimestamp( Left( myImportedTimestamp ; 11 ) )
Doing conversion to Unix format, either programmatically or through display on the resultingTimestamp field on a Layout.
If you don't have FileMaker:
Take the left 11 digits of the FileMaker timestamp.
Subtract 62135596800 from the FileMaker timestamp to get the Unix (epoch) timestamp.
(Verified by taking the same date in each and subtracting the FileMaker date from the Unix date.)
Convert epoch time to human readable, for example according to one of the formulas found in the "Convert from epoch to human readable date" section of epochconverter.com.
To get your date:
create a calculation field with the following calculation:
TimeStamp/864000000000+1
set the return type to Date.
Also, I think the extra zeroes are fractions of a second, regardless the given formula deals with these.
I have create one field in sql server database as nvarchar datatype and store some date like 'd/MM/yyyy' and 'dd/MM/yyyy' format previously. Now i want to get all data in 'dd/MM/yyyy' format using query it is possible?
You can cast the field to datetime in the query:
select cast(YourField as datetime)
from YourTable
where isdate(YourField) = 1
The where isdate(YourField) = 1 part is necessary to filter out rows where the value is no valid date (it's a nvarchar field, so there could be things like abc in some rows!)
But you should really change the field to datetime in the long term, as already suggested by Christopher in his comment.
Casting like described above is always error-prone because of the many different data formats in different countries.
For example, I live in Germany where the official date format is dd.mm.yyyy.
So today (December 9th) is 9.12.2011, and running select cast('9.12.2011' as datetime) on my machine returns the correct datetime value.
Another common format is mm/dd/yyyy, so December 9th would be 12/9/2011.
Now imagine I have a nvarchar field with a date in this format on my German machine:
select cast('12/9/2011' as datetime) will return September 12th (instead of December 9th)!
Issues like this can easily be avoided by using the proper type for the column, in this case datetime.