While some methods of SqlExpression<T> supports up to 15 generic parameters (Where, And, Or) others like Select, SelectDistinct and GroupBy only supports a couple. When building complex queries, it's easy to select data from more than 7 tables, or group by fields from more than 4 tables.

Could you implement more Select, SelectDistinct and GroupBy overloads like you did for Where, And and Or?

There is no specific number of parameters needed, but I think that the default 15 is a good start.