Data is not working

i make two table in sqlite browser, but it's not working. please help me! CREATE TABLE DanhMuc ( MaDM INTEGER NOT NULL, Ten TEXT NOT NULL, HinhAnh INTEGER, PRIMARY KEY(MaDM) );

CREATE TABLE SanPham ( MaSP TEXT NOT NULL, Ten TEXT NOT NULL, DonGia NUMERIC NOT NULL, DonViTinh TEXT NOT NULL, MaDM_PK INTEGER NOT NULL, HinhAnh INTEGER, PRIMARY KEY(MaSP), FOREIGN KEY(MaDM_PK) REFERENCES DanhMuc(MaDM) );