CREATE TABLE medico
    (num_cedula serial NOT NULL UNIQUE,
     nome varchar(20) NOT NULL,
     especialidade varchar(20) NOT NULL,
     PRIMARY KEY(num_cedula));

CREATE TABLE consulta
    (num_cedula serial NOT NULL,
     num_doente serial NOT NULL,
     data_consulta date NOT NULL,
     nome varchar(20) NOT NULL,
     CHECK(EXTRACT(DOW FROM data_consulta) NOT IN (6,0)),
     UNIQUE(num_doente,data_consulta,nome),
     FOREIGN KEY(nome) REFERENCES instituicao(nome) ON UPDATE CASCADE,
     FOREIGN KEY(num_cedula) REFERENCES medico(num_cedula) ON UPDATE CASCADE,
     PRIMARY KEY(num_cedula,num_doente,data_consulta));

CREATE TABLE analise
    (num_analise serial NOT NULL UNIQUE,
     especialidade varchar(20) NOT NULL,
     num_cedula serial ,
     num_doente serial ,
     data_analise date ,
     data_registo date NOT NULL,
     nome varchar(20) NOT NULL,
     quant integer NOT NULL,
     inst varchar(20) NOT NULL,
     CONSTRAINT fk_analise FOREIGN KEY(num_cedula,num_doente,data_analise) REFERENCES consulta(num_cedula,num_doente,data_consulta) ON UPDATE CASCADE,
     FOREIGN KEY(inst) REFERENCES instituicao(nome) ON UPDATE CASCADE,
     PRIMARY KEY(num_analise)); 

这是我的代码，但是当我尝试使用num_cedula，num_doente，data_analise作为NULL插入另一个“ analise”时，会出现此错误（“ ERROR：列“ num_cedula”中的null值违反了非null约束详细信息：失败行包含（32 ，Ortopedia，null，null，null，2019年12月2日，glicemia，176，Instituicao1）。SQL状态：23502“），我真的不知道为什么。另外，这是我使用的插入代码：

INSERT INTO analise VALUES(32,'Ortopedia',NULL,NULL,NULL,'2019-12-02','glicemia',176,'Instituicao1');