Splitting and Analyzing data - sql

Question

I have a field that sometimes contains a string like the following: 2/23/2013 12:25:55~45
I need to split the string at the ~ and identify if what's left of the ~ is a valid date time value and what's right of the ~ is a valid integer. Basically what i want to return is a True/False whether those conditions are correct.
Keep in mind that the field could contain nulls, could contain any other type of data, and it could contain multiple tildes. In all cases I need to return false. The only time I need to return true is when the field contains a date/time value, a single tilde, and a whole number.

Answer 1

In SQL Server, you could do:
select (case when col like '%~%'
then (case when isdate(left(col, charindex('~', col) - 1)) = 1 and
isnumeric(substring(col, charindex('~', col)+1, 1000)) = 1 and col not like '%~%.%' and col not like '%~%e%'
then 1
else 0
end)
else 0
end) as IsFunkyFormat, substring(col, charindex('~', col)+1, 1000), left(col, charindex('~', col) - 1)
The nested case is to prevent errors when the separator is not found. The not like expressions are intended to rule out number formats that are not integers.

Answer 2

This question is trickier than it looks because it would be easy to get wrong, or to write it in such a way that it works now, for your given set of data, but fails to work for other sets of data.
If this is the data you are storing in your database, I strongly encourage you to learn about database normalization. One tenet of normalization is that you only store one value in a column. In this case, you are storing a datetime and an integer value in the same column. It would be far better to store the data in multiple columns.
That being said, I know that there are times when you are given some raw data that you need to import in to your database. Often times, we cannot control the raw data that we are given, so we must make do with SQL gymnastics. In this particular case, there are several different types of back-flips that will be useful.
Determine the number of ~ characters in your string.
splitting the data on the tilde.
Making sure one of the values is a datetime
Making sure the other value is an integer.
Only 1 of the 4 items is built in to SQL Server. There is a function names IsDate that takes a string parameter and returns a bit indicating whether the date represented by the string can be converted to a date.
To determine the number of ~ in your string, the trick is to determine the length of the string with the tilde's, and the length of the string without the tilde's. We can determine which rows contain a single tilde by doing this:
When Len(Data) = Len(Replace(Data, '~', '')) + 1
The other tricky problem to solve is to determine if a string represents a whole number. There are multiple ways of doing this, but my favorite method is to concatenate hard coded values to your data and then test for numeric. For example, the IsNumeric function will return true for the string 1e4 because the e represents scientific notation and 1e4 could be interpreted as 1000. So if you do this:
IsNumeric(Data + 'e0')
This will return false for scientific notation because the data would be something like 1e4, which is concatenated to 'e0' to get '1e4e0' which is not numeric. Similarly, we can concatenate .0 to the string to check for fractional numbers. If your data is 45.2 (which is numeric) and you concatenate .0 to it, you get '45.2.0' which is not numeric. You can also add '-' to the test to check for positive numbers. '-20' is numeric, but '-' + '-20' (which is '--20') is not numeric.
Select YourColumnHere,
Len(Replace(YourColumnHere, '~', '')) + 1,
Case When Len(YourColumnHere) = Len(Replace(YourColumnHere, '~', '')) + 1
Then
Case When IsDate(Left(YourColumnHere, CharIndex('~', YourColumnHere)-1)) = 1
Then
Case When Right(YourColumnHere, Len(YourColumnHere)-CharIndex('~', YourColumnHere)) > ''
Then IsNumeric('-' + Right(YourColumnHere, Len(YourColumnHere)-CharIndex('~', YourColumnHere)) + '.0e0')
Else 0
End
Else 0
End
Else 0
End
From YourTableNameHere