substring
fun Expression<StringValue>.substring(startIndex: Expression<IntValue>, endIndex: Expression<IntValue>? = null): Expression<StringValue>(source)
fun Expression<StringValue>.substring(startIndex: Int, endIndex: Int? = null): Expression<StringValue>(source)
Returns a substring from this string from the startIndex (inclusive) to the end of the string if endIndex is not specified or null, otherwise to endIndex (exclusive).
A UTF-16 surrogate pair counts as a single position.