Question

If I have the following nvarchar variable – BTA200, how can I extract just the BTA from it?

Also, if I have varying lengths such as BTA50, BTA030, how can I extract just the numeric part?

Answer 1

I would recommend a combination of PatIndex and Left. Carefully constructed, you can write a query that always works, no matter what your data looks like.

Ex:

Declare @Temp Table(Data VarChar(20))  Insert Into @Temp Values('BTA200') Insert Into @Temp Values('BTA50') Insert Into @Temp Values('BTA030') Insert Into @Temp Values('BTA') Insert Into @Temp Values('123') Insert Into @Temp Values('X999')  Select Data, Left(Data, PatIndex('%[0-9]%', Data + '1') - 1) From   @Temp 

PatIndex will look for the first character that falls in the range of 0-9, and return it’s character position, which you can use with the LEFT function to extract the correct data. Note that PatIndex is actually using Data + ‘1’. This protects us from data where there are no numbers found. If there are no numbers, PatIndex would return 0. In this case, the LEFT function would error because we are using Left(Data, PatIndex – 1). When PatIndex returns 0, we would end up with Left(Data, -1) which returns an error.

There are still ways this can fail. For a full explanation, I encourage you to read:

Extracting numbers with SQL Server

That article shows how to get numbers out of a string. In your case, you want to get alpha characters instead. However, the process is similar enough that you can probably learn something useful out of it.