internal static String CompileLimitClause(this Expression This) =>
     "LIMIT " + This.CompileExpr();
 internal static String CompileOffsetClause(this Expression This) =>
     "OFFSET " + This.CompileExpr();
 internal static String CompileWhereClause(this Expression This)
 {
     var compiled = This.CompileExpr();
     return compiled.Length > 0 ? "WHERE " + This.CompileExpr() : "";
 }