SQL Varchar convert to Date - Sybase - sql

Question

I am using Sybase IQ and have the following stored as a varchar:
01October 2010
I want to convert this from varchar to date datatype with the following format:
yyyy-mm-dd eg.2010-10-01
How would I write this SQL statement? Thanks in advance.

Answer 1

With difficulty. There's a reason you should never store dates and times as strings.
It's been awhile since I've used Sybase, but what we need to do is get the field into YYYY-MM-DD format, and then pass it to the DATE() or DATETIME() function.
Let's assume the first two characters are always the day of the month, and the last 4 characters are the year. That means everything in between is the month. Let's also assume that there are no leading or trailing spaces. If either of these assumptions fails, then the query will fail.
Then you can do something like this:
SELECT DATE (
RIGHT(UnnamedField,4) + '-' +
CASE LTRIM(RTRIM(SUBSTRING(Unnamed,3,LEN(Unnamed) - 6)))
WHEN 'January' THEN '01'
WHEN 'February' THEN '02'
WHEN 'March' THEN '03'
.
.
.
WHEN 'December' THEN '12'
END + '-' + LEFT(UnnamedField,2)
)
FROM UnnamedTable
Note that, as others have mentioned, the date data type is not a formatted datatype. If possible you should format it in your application. If you must do it in the query, use the CONVERT() function.

Answer 2

Sybase is able to convert a string to a date. So if you use substring to extract the date into a format that IQ can convert, then you can just use the convert() function.
Here's an example of how to do it:
Sample data:
create table #tmp1 (col1 varchar(100))
insert #tmp1 values ('01October 2010')
Query to convert the value to a date:
select
convert
(
date,
(
substring(col1, 3, charindex(' ', col1) - 2) -- Month
+ substring(col1, 1, 2) -- Day
+ substring(col1, charindex(' ', col1), 5) -- Year (include the leading space)
)
)
from #tmp1
Now that the value is in a date format, you can use the convert function to convert the date datatype to string, using your specified format. The default output for a date datatype is yyyy-mm-dd already.
Edit: After taking a look at #BaconBits' answer, I've realized that I could simplify the query a bit by using the substring function wrappers left, right, and the convert wrapper of date. It's the same logic; but using the simplified wrappers might make it easier to understand.
select
date
(
substring(col1, 3, charindex(' ', col1) - 2) -- Month
+ left(col1, 2) -- Day
+ ' ' + right(col1, 4) -- Year (include the leading space)
)
from #tmp1