Subfield() is a great function for splitting a long string into seperate fields. You can use this to split out a date or anything where you have a common delimeter in a string.

For example. If you have the string

field name: TextString

line 1: Big_Frogs_Are_Yummy

You may want to split this out into 4 seperate fields.

subfield(TextString, '_', 1) as FirstWord,

subfield(TextString, '_', 2) as SecondWord,

subfield(TextString, '_', 3) as ThirdWord,

In this example the delimiter is ‘_’ as that is what splits up the words. The number is the position you want to take.

So the above will output the following for your new fields

FirstWord = Big

SecondWord = Frogs

ThirdWord = Are

Easy!

The syntax:,

SubField(text, delimiter[, field_no ])

Official Documentation