I am querying a SQLite database table as follows:
SELECT MAX(Date) from Intra360 WHERE Date <= "05/04/2013 00:00"
The right record in return should be the number 47, i.e. 04/04/2013 23:00:
However, the execution of this statement returns a different value:
I confess I know almost nothing about SQL, but this outcome is strange. Where am I being wrong?
NOTE "Intra360" is the name of the table and the field containing the dates is called "Date"
ADDITIONAL NOTE what I need is the closest available date to a user input. It is a Python program which is making some analysis but when the user inputs the dates is not necessarily true they will exist in the database. So I'm just trying to re-select them in a way that the proper SQL statement that will load the data to be used in the analysis won't fail execution because of the missing record. So "05/04/2013 00:00" is the user input, and the query should be done hence starting from 04/04/2013 (and not definetely 04/06/2013).
The comparisons are performed on strings with alphabetical ordering, not on datetime stamps with chronological ordering.
Store your datetimes in a format that compares the way you want. For example, unix epoch timestamps and ISO 8601 yyyy-MM-dd'T'HH:mm:ss datetimes have this property.
If you cannot influence how the data is stored, you can use substr() to mangle the timestamps in SQL. See e.g. Sqlite convert string to date for more.
Related
I am trying to fetch the records which are having all time stamp columns.
I am using the following query to fetch the products that are created between the final date and (final date - 30) days, i.e products created during the last 30 days that fall in the 'final date' range.
I have products that are created on 30-OCT-2014. For the same products, the initiated date is 12-NOV-2014. However they are not being fetched when I using the below query.
SELECT A.ROW_ID,
A.PROD_NAME
FROM PROD A,
PROD_REL B
WHERE A.ROW_ID = B.PAR_ROW_ID
AND TO_DATE(A.CREATED_DT,'YYYY-MM-DD') BETWEEN (TO_DATE(B.FINAL_DATE,'YYYY-MM-DD') - 30)
AND (TO_DATE(B.FINAL_DATE,'YYYY-MM-DD'));
So, could you please let me know if I am missing something?
Here is a link to a SQLFiddle that demonstrates the problem.
… or just fix your format string TO_DATE(A.CREATED,'DD-MON-YYYY')
SQL Fiddle
Storing dates as DATE, is , of course, always a good starting point.
Since your data types are all dates, there is no need to use to_date. It's harmful, in fact, since to_date doesn't take a date as a parameter. Oracle has to do an implicit conversion from a date to a string, using your session's NLS_DATE_FORMAT which gets passed in to to_date and converted back to a date using the explicit format mask you specified. If the two conversions aren't using the same format mask, bad things happen.
Your WHERE clause just needs to be
AND a.created_dt BETWEEN b.final_date - 30
AND b.final_date
If I make that change, your SQLFiddle returns two rows
i'm new to MS Access..
one of my Access table CHECKOUT having a column name CHECK-TIME with Date/time data type
values in that column are like 7/15/2013 10:56:22 AM,9/19/2013 6:54:37 PM....
i want to select the data based on date like `7/15/2013'
how to write the query for this task ???
thanks in advance..
First off, the way to specify date literals is with hash (#) not any form of quote or backtick.
Secondly, you can't do LIKE comparisons with dates, not that I've ever seen anyway.
Thirdly, it's always best to specify dates in yyyy-mm-dd format because it's an unambiguous format.
This example should give you what you need:
SELECT
*
FROM
CHECKOUT
WHERE
datevalue([CHECK-TIME]) = #2013-07-15#
The datevalue() function takes a parameter, usually a string but in this case a datetime, and converts it to a date, thus stripping off the time. This allows us to check for equality against a date literal.
I have to run column checks for data consistency and the only thing that is throwing off my code is checking for character lengths for dates between certain parameters.
SEL
sum(case when ( A.date is null or (character_length(A.date) >8)) then 1 else 0 end ) as Date
from
table A
;
The date format of the column is YYYY-MM-DD, and the type is DA. When I run the script in SQL Assistant, I get an error 3580 "Illegal use of CHARACTERS, MCHARACTERS, or OCTET_LENGTH functions."
Preliminary research suggests that SQL Assistant has issues with the character_length function, but I don't know how to adjust the code to make it run.
with chareter length are you trying to get the memory used? Becuase if so that is constant for a date field. If you are trying to get the length of the string representation i think LENGTH(A.date) will suffice. Unfortanatly since teradata will pad zeros on conversions to string, I think this might always return 10.
UPDATE :
Okay so if you want a date in a special 'form' when you output it you need to select it properly. In teradata as with most DBs Date are not store in strings, but rather as ints, counting days from a given 'epoch' date for the database (for example the epoch might be 01/01/0000). Each date type in teradata has a format parameter, which places in the record header instructions on how to format the output on select. By default a date format is set to this DATE FROMAT 'MM/DD/YYYY' I believe. You can change that by casting.
Try SELECT cast(cast(A.date as DATE FORMAT 'MM-DD-YYYY') as CHAR(10)) FROM A. and see what happens. There should be no need to validate the form of the dates past a small sample to see if the format is correct. The second cast forces the database to perform the conversion and use the format header specified. Other wise what you might see is the database will pass the date in a date form to SQL Assitant and sql assitant will perform the conversion on the application level, using the format specified in its own setting rather then the one set in the database.
I have a table with two columns, all of them are datetime value
Such as, Column A with value ‘07/09/2012 14:13:34’
Now, I want to update column A to yyyymmdd by statement
Update Change_Date
SET A = CONVERT(VARCHAR(8),A,112)
It shows succsessful message but with no effect (no update value to 20120907) in my table Change_Date.
Any help will be greated, thank you!
A datetime fields saves a date time. How you see that date time is a result of the tool you're using to inspect the data, whether it is Management Studio, or your own software that's printing something from the database.
I strongly recommend keeping it as a datetime field. This will allow you to do date-related operations, such as subtractions and comparisons. If you want to change how your users see the date, then format your date at the presentation layer.
What's happening in the code you've posted is that you're setting the value of A to the same date that it already is. The fact that you're setting that value by means of a string in another format has no relation, SQL server will always have to parse your string input into a date that it can understand. This is why you're not getting an error message. The operation is working, only it's not changing anything.
You can select the date column in specified format or make a view which selects the column value in yyyymmdd format:
SELECT CONVERT(VARCHAR(8), A, 112) FROM Change_Date
It's because the datatype of the column is DATE or DATETIME and it has specific format. If you want to update the column with specific format, make another column and make its datatype VARCHAR. I believe 112 is yyyymmdd format.
I strongly suggest that you keep it AS IS. Database is the storage of data and not for viewing purposes. It is easy to perform task for dates if your data type is DATETIME or DATE. If for instance you want to retrieve the dates with specific format, that's the time you convert your date.
Hope this makes sense.
Problem: I have a large database table (~500k records) which has a list of dates stored in a varchar2(15) column. These dates are stored in varying formats, ie. some are yyyy-mm-dd, some are mm/dd/yyyy, some are dd/mm/yy, some are mm/dd/yy, etc. Ie:
1994-01-13
01/13/1994
01/13/94
13/01/94
13/01/1994
etc
I need to be able to shift these dates slightly, for example to add 30 days to each date. (This is an oversimplification of my objective but it's easier to explain this way).
If all the dates were formatted consistently, I would achieve this as follows:
UPDATE history_table
SET some_date_col =
to_char(to_date(some_date_col, 'mm/dd/yyyy')+30, 'mm/dd/yyyy')
WHERE some_date_col IS NOT NULL;
Due to the size of the database, I cannot afford to loop through the values one by one and parse the date value. Can anyone suggest a means to accomplish this without loops, ie with a mass UPDATE statement?
Are the formats of these dates really that important? They should be datetime columns. Then you could just use date math functions on that field.
well, you've got a real problem here.
07/07/1994 is valid for 'MM/DD/YYYY' and 'DD/MM/YYYY'
However, outside of that issue, you can try nesting decodes.
I entered the following dates into a varchar field:
01/12/2009, 01-12-2009, 2009-01-12, 01/12/09
and using the below, I was consistently returned 1/12/2009. You'll have to figure out all the patterns possible and keep nesting decodes. The other thing you could do is create a function to handle this. Within the function, you can check with a little more detail as to the format of the date. It will also be easier to read. You can use the function in your update statement so that should be faster than looping through, as you mentioned.
(for what its worth, looping through 500k rows like this shouldn't take very long. I regularly have to update row by row tables of 12 million records)
select mydate,
decode(instr(mydate,'-'),5,to_date(mydate,'YYYY-MM-DD'),3,to_date(mydate,'MM-DD-YYYY'),
decode (length(mydate),8,to_date(mydate,'MM/DD/YY'),10,to_date(mydate,'MM/DD/YYYY')))
from mydates;
and here is the update statement:
update mydates set revdate = decode(instr(mydate,'-'),5,to_date(mydate,'YYYY-MM-DD'),3,to_date(mydate,'MM-DD-YYYY'),
decode (length(mydate),8,to_date(mydate,'MM/DD/YY'),10,to_date(mydate,'MM/DD/YYYY')))
IMHO, you have a bigger problem:
If some dates are dd/mm/yyyy and some are mm/dd/yyyy how can you difference which format applies for certain date?
for example, how can I know if a value "12/09/2008" means December or September?