I’ve a table with products in groups. Each product form the same group has a name that starts with the same sub string. For example:

group1|”carpentry manual first book”

group1|”carpentry manual second book”

group1|”carpentry manual second book appendix”

group1|”carpentry manual third book”

group2|”blacksmith’s manual first book”

etc…

I need a function that returns “carpentry manual”, that is to say the longest common sub string of group’s records, starting from the first character.

Thanks!!