C new a Criteria.

NewPageRet new a PageRet.

P new a Page.

Criteria wrap a group of column, value and operator such as name = 20.

Order by Col Sort.

Page a sql expression builder for order by clause.

PageRet wrap page query result.

Where concat children clauses with one of logic operators And, Or, Append.

Base sql expression.

Q used for building sql expression.

String is an alias of string.