I have a value in field called "postingdate" as string in 2009-11-25, 12:42AM IST format, in a table named "Post".
I need the query to fetch the details based on date range. I tried the following query, but it throws an error. Please guide me to fix this issue. Thanks in advance.
select postingdate
from post
where TO_DATE(postingDate,'YYYY-MM-DD')>61689
and TO_DATE(postingDate,'YYYY-MM-DD')<61691
As you've now seen, trying to perform any sort of query against a string column which represents a date is a problem. You've got a few options:
Convert the postingdate column to some sort of DATE or TIMESTAMP datatype. I think this is your best choice as it will make querying the table using this field faster, more flexible, and less error prone.
Leave postingdate as a string and use functions to convert it back to a date when doing comparisons. This will be a performance problem as most queries will turn into full table scans unless your database supports function-based indexes.
Leave postingdate as a string and compare it against other strings. Not a good choice as it's tough to come up with a way to do ranged queries this way, as I think you've found.
If it was me I'd convert the data. Good luck.
In SQL Server you can say
Select postingdate from post
where postingdate between '6/16/1969' and '6/16/1991'
If it's really a string, you're lucky that it's in YYYY-MM-DD format. You can sort and compare that format as a string, because the most significant numbers are on the left side. For example:
select *
from Posts
where StringDateCol between '2010-01-01' and '2010-01-02'
There's no need to convert the string to a date, comparing in this way is not affected by the , 12:42AM IST appendage. Unless, of course, your table contains dates from a different time zone :)
You will need to convert your string into a date before you run date range queries on it. You may get away with just using the string if your not interested in the time portion.
The actual functions will depend on your RDBMS
for strings only
select * from posts
where LEFT(postingDate,10) > '2010-01-21'
or
for datetime ( Sybase example)
select * from posts
where convert(DateTime,postingDate) between '2010-01-21' and '2010-01-31'
Related
I have a date column in string format stored in the big query. It is showing as dd-mm-yyyy.
I want to change it to yyyy-mm-dd but keep it in string format.
Such as 10-01-2023 to 2023-01-10.
I am not sure how to do it, any help would be appreciated.
Thanks
Keeping date as date data type makes more sense for any further calculations.
But if you really need it all in strings, here is how you can do it.
You can all do it in one go, but I've split into separate subqueries for your understanding.
select cast(actual_date as string) as reformatted_string_date from (
select parse_date('%m-%d-%Y', string_date) as actual_date
from (select '10-01-2023' as string_date )
)
I should preface my question by saying I am very new to SQL (or any programming involving databases). I started learning SQL a couple of weeks ago when I decided to take on a data project.
I have been using SSMS in wrangling large tables in comma-separated text file format. I need to be able to sort by dates, and the current format is mmddyyyy, but when I try to sort by date it does not work.
I know that converting dates is something that gets asked a lot around here, but I haven't found any solutions that explain things for a newb like myself.
So far my guesses for a solution are to use the CONVERT or CAST solutions, but I'm not sure if that is the right approach. I have found several CAST/CONVERT posts but none have really applied to my situation.
I hate to have this as my first question, but I'd thought I'd take some down vote bullets if it means I could figure this out. Thank you.
Sample of what I'm trying to do:
SELECT *
FROM [databasename].[dbo].[table1]
WHERE [ column1] > 01012017;
I get the entire table back, unsorted.
Since your:
SELECT *
FROM [databasename].[dbo].[table1]
WHERE [ column1] > 01012017;
does not error, we could say that the [column1]'s datatype is either a character type (like VARCHAR, char), or datetime.
Since you are getting back all the data and I would think you don't have data in the future, it should be a varchar (or char) - with datetime that means 1900-01-01 + 1012017 days.
To make it a datetime you need to 'cast' your column1 which is in mmddyyyy form by first converting it to yyyymmdd style (which would work under any date and language setting):
cast(right([column1],4)+substring([column1],1,2)+substring([column1],3,2) as datetime)
and you would write that 01012017 as a string (quotes around) and also again in yyyymmdd format (it would be implicitly casted to datetime):
'20170101'
So your SQL becomes:
SELECT *
FROM [databasename].[dbo].[table1]
WHERE cast(right([column1],4) +
substring([column1],1,2) +
substring([column1],3,2) as datetime) > '20170101';
Having a date\datetime column as varchar and using like this would render the ability to use simple indexes but that is another matter. For now, this would return the data you want.
Assuming your column's datatype is [Date], try something similar to:
SELECT *
FROM [databasename].[dbo].[table1]
WHERE FORMAT([column1],'dd/MM/yyyy') >'01012017'
If it's string format, you'll have to use CONVERT() to convert the column to Date with a query like
SELECT *
FROM [databasename].[dbo].[table1]
WHERE CONVERT(NVARCHAR(10), [Column1], 112) >'01012017'
Refer to this W3Schools article if you need more help with the CONVERT clause
There is this strange error in sql query.
The query is something like this.
select * from student where dob between '20150820' and '20150828'
But in the database the column of dob is varchar(14) and is in yyyyMMddhhmmss format,Say my data in the row is (20150827142545).If i fire the above query it should not retrive any rows as i have mentioned yyyyMMdd format in the query.But it retrives the row with yesterday date (i.e 20150827112535) and it cannot get the records with today's date (i.e 20150828144532)
Why is this happening??
Thanks for the help in advance
You can try like this:
select * from student
where convert(date,LEFT(dob,8)) between
convert(date'20150820') and convert(date,'20150828'))
Also as others have commented you need to store your date as Date instead of varchar to avoid such problems in future.
As already mentioned you would need to use the correct date type to have between behave properly.
select *
from student
where convert(date,LEFT(dob,8)) between '20150820' and '20150828'
Sidenote: You don't have to explicitly convert your two dates from text as this will be done implicitly as long as you use an unambiguous date representation, i.e. the ISO standard 'YYYYMMDD' or 'YYYY-MM-DD'. Of course if you're holding the values in variables then use date | datetime datatype
declare #startdate date
declare #enddate date
select *
from student
where convert(date,LEFT(dob,8)) between #startdate and #enddate
Sidenote 2: Performing the functions on your table dob column would prevent any indexes on that column from being used to their full potential in your execution plan and may result in slower execution, if you can, define the correct data type for the table dob column or use a persistent computed column or materialised view if your performance is a real issue.
Sidenote 3: If you need to maintain the time portion in your data i.e. date and time of birth, use the following to ensure all records are captured;
select *
from student
where
convert(date,LEFT(dob,8)) >= '20150820'
and convert(date,LEFT(dob,8)) < dateadd(d,1,'20150828')
All you have to do is to convert first the string to date.
select *
from student
where dob between convert(date, '20150820') and convert(date, '20150828')
Why is this happening?
The comparison is executed from left to right and the order of characters is determined by the codepage in use.
Sort Order
Sort order specifies the way that data values are sorted, affecting
the results of data comparison. The sorting of data is accomplished
through collations, and it can be optimized using indexes.
https://msdn.microsoft.com/en-us/library/ms143726.aspx
There are problems with between in T-SQL.
But if you want a fast answer convert to date first and use >= <= or even datediff to compare - maybe write a between function yourself if you want the easy use like between and no care about begin and start times ...
What do BETWEEN and the devil have in common?
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.
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?