I am having a string of almost 1600 characters in a column, of which I need to extract out a substring. The substring which needs to be extracted is of the type

1A…………..2A…………..3A…………..

Every string here is of 16 chars starting from 1A, 2A, 3A, 4A etc.
The combination of 1A, 2A, 3A is a valid one and should ideally be present in the string always.

If the above pattern is not matching then the string shouldn’t be extracting, but rather should throw an error.

Any suggestions ?