create a Rigger to allow you to lend a book only to students who have 'MT' status

Question

the teacher asked to make a Rigger in postgresql, only that can not do no if someone can help me, create Function emprestimo_book() Returns Trigger language plpgsql as $$ Begin if( Insert Loan Bookbook

Return new; end; $$ data set, create schema provaII set schema 'probable';

CREATE TABLE STUDENT ( CDALUNO INTEGER NOT NULL, NAME VARCHAR(40) , NMATRICULA VARCHAR(15), STATUS CHAR(2) );

Insert into Aluno values (1, 'Antonio Bandeiras', '00010-2018','MT'), (2, 'Bill Gates', '00002-2018', 'RP') , (3, 'Steve Snick', '00003-2018', 'AP') , (4, 'Linus Torvals', '00404-2018','AM')

CREATE TABLE COURSE ( CDCURSO INTEGER NOT NULL, NAME VARCHAR(20), NUMERIC VALUE(7,2));

Insert into curso values(10, 'ADS', 800.00), (11, 'Quimica',900.00), (12, 'Agronomy', 1000.00), (13, 'Agroindustria', 1100.00)

CREATE TABLE PROFESSOR ( CDPROFESSOR INTEGER NOT NULL, NAME VARCHAR(40));

Insert into professor values (20, 'MAXUEEL SANTOS'), (21, 'ANTOIN LIMA') (22, 'GEORGINA COTRIM') , (23, 'PAULITA FERREIRA')

CREATE TABLE DISCIPLINE ( CDDISCIPLINA INTEGER NOT NULL, NOMEDISCIPLINA varchar(40), CDPROFESSOR INTEGER, NUMERIC VALUE(7,2));

Insert into DISCIPLINA values(30, 'ALGORITHM',20,500.00), (31, 'DATABASE',21, 600.00), (32, 'TABD',21, 600.00)

CREATE TABLE SEMESTER ( CDSEMESTRE INTEGER NOT NULL, VARCHAR YEAR(15));

INSERT INTO SEMESTER VALUES(50,'2017.1'), (51,'2017.2') , (52,'2018.1') , (53,'2018.2')

CREATE TABLE TURMA ( CDTURMA INTEGER NOT NULL, CLASS VARCHAR(20)) ;

INSERT INTO CLASS VALUES(60, 'PROGRAMMERS'), (61,'ANALYSTS')

CREATE TABLE MATRICULA ( CDMATRICULA INTEGER NOT NULL, CDCURSO INTEGER, STUDENT OFFICER INTEGER, CDSEMESTRE INTEGER, NUMERIC VALUE(7,2), CDTURMA INTEGER);

INSERT INTO matricula values( 100, 10, 1, 50,300.00,60), ( 101, 10, 2, 50,400.00,60), ( 102, 12, 3, 50,500.00,61), ( 103, 13, 4, 50,500.00,61),

                        ( 104, 10, 1, 51, 300.00, 60),
                        ( 105, 10, 2, 51, 400.00, 60),
                        ( 106, 12, 3, 51, 500.00, 61),                         
                        ( 107, 13, 4, 51, 500.00, 61),

                        ( 108, 10, 1, 52, 300.00, 60),
                        ( 109, 10, 2, 52, 400.00, 60),
                        ( 110, 12, 3, 53, 500.00, 61),                         
                        ( 111, 13, 4, 53, 500.00, 61)

CREATE TABLE MATDISCIPLINA ( CDMATDISCIPLINA INTEGER NOT NULL, CDMATRICULA INTEGER, CDDISCIPLINA INTEGER MEDIA NUMERIC(7,2), STATUS CHAR(2), CDPROFESSOR INTEGER, NUMERIC VALUE(7,2));

insert into matdisciplina(cdmatdisciplina,cdmatricula,cddisciplina, status,valor) 
       values( 1,100,30,'AP', 500.00),
             ( 2,100,31,'AP', 600.00),
             ( 3,100,32,'AP', 600.00),
             ( 4,100,33,'AP', 500.00),

             ( 5,101,30,'RP', 500.00),
             ( 6,101,33,'RP', 350.00),
             ( 7,101,34,'RE', 400.00),

             ( 8,102,30,'MT', 350.00),
             ( 9,102,31,'MT', 300.00),

             (10,103,30,'MT', 660.00),
             (11,103,32,'MT', 760.00)

CREATE TABLE NOTE ( CDNOTA INTEGER NOT NULL, CDMATDISCIPLINA INTEGER, NUMERIC NOTE(7,2), REFERENCE VARCHAR(20), STATUS CHAR(2));

Insert into note values (1, 1, 8.00, 'Av I', 'AP') , (2, 1, 4.00, 'AV II', 'RP') , (3, 1, 3.00, 'AV III', 'RP'), (4, 2, 6.00, 'Av I', 'RP') , (5, 2, 4.00, 'AV II', 'RP') , (7, 3, 4.00, 'Av I', 'RP') , (8, 3, 4.00, 'AV II', 'RP') , (9, 4, 8.00, 'Av I', 'AP') , (10, 4, 4.00, 'AV II', 'RP')

create table book ( Cdlivro INTEGER NOT NULL, nomelivro varchar(40));

Insert into book values (1, 'TABD'), (2, 'SO') and (3, 'BD') , (4, 'BOLSONARO'')

create table emprestimolivro ( Cdemplivro INTEGER NOT NULL, Cdmattricula INTEGER, cdinteger book, Statusemp CHAR(2));

Insert into Businessbook values (1, 100,1,'EM'), (2, 100,2,'DE'), (3, 100,3,'EM') and (4, 101,4,'DE')