In reply to Hongjie Liu.

You can ask questions, discuss programs, and share data at the SAS Support Communities. By definition, a restricted quadratic model is a quadratic model that has restrictions on the parameters. So, no, I would not use an EFFECT statement for restricted quadratic regression. If you have linear restrictions, you can use PROC REG or PROC NLIN (see this article). For nonlinear constraints, I would use optimization in PROC IML or PROC OPTMODEL.