multi table content selection - php

Question

I am working on Exam System. I have (student),(student_test),(test),(departments) tables having relationship with each others. When every student log in there is a link called take test which will redirect them to take test page.
Question: How can I get all the available related to student department tests from test table only if the student have not attended the test or in other words how to get all the test from test table that student haven't taken?
$select=$connection->query("SELECT
student.std_id,
student.department,
test.depart_id,
test.test_id,
test.test_name,
test.test_from,
std_test.stdid,
std_test.std_test_id
FROM student
INNER JOIN test
ON student.department = test.depart_id
INNER JOIN std_test
ON std_test.std_test_id <> test.test_id
I tried this code as well but not results.
SELECT
student.std_id,
student.department,
test.depart_id,
test.test_id,
test.test_name,
test.test_from,
std_test.stdid,
std_test.std_test_id
FROM student
INNER JOIN test
ON student.department = test.depart_id
INNER JOIN std_test
ON std_test.std_test_id <> test.test_id
WHERE test.test_id <> std_test.std_test_id AND student.std_id <> std_test.stdid
Schema Script
CREATE TABLE student (
std_id int(11) NOT NULL AUTO_INCREMENT,
name varchar(50) NOT NULL,
f_name varchar(50) NOT NULL,
department int(11) NOT NULL,
semester varchar(255) NOT NULL,
pass varchar(255) NOT NULL,
email varchar(60) NOT NULL,
rollnumber varchar(20) NOT NULL,
PRIMARY KEY (std_id),
INDEX department (department),
UNIQUE INDEX email (email),
CONSTRAINT student_ibfk_1 FOREIGN KEY (department)
REFERENCES departments (dep_id) ON DELETE RESTRICT ON UPDATE RESTRICT
)
ENGINE = INNODB
AUTO_INCREMENT = 8
AVG_ROW_LENGTH = 8192
CHARACTER SET latin1
COLLATE latin1_swedish_ci;
CREATE TABLE test (
test_id int(11) NOT NULL AUTO_INCREMENT,
test_name varchar(80) NOT NULL,
test_date varchar(30) NOT NULL,
test_from datetime NOT NULL,
test_to datetime NOT NULL,
test_code varchar(30) NOT NULL,
test_conducter varchar(30) NOT NULL,
test_duration int(11) NOT NULL,
total_question int(11) NOT NULL,
session varchar(50) DEFAULT NULL,
subject_id int(11) NOT NULL,
semester_id int(11) NOT NULL,
depart_id int(11) NOT NULL,
status varchar(50) NOT NULL,
PRIMARY KEY (test_id),
INDEX depart_id (depart_id),
INDEX semester_id (semester_id),
INDEX subject_id (subject_id, semester_id, depart_id),
CONSTRAINT test_ibfk_1 FOREIGN KEY (subject_id)
REFERENCES subjects (id) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT test_ibfk_2 FOREIGN KEY (semester_id)
REFERENCES semester (sem_id) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT test_ibfk_3 FOREIGN KEY (depart_id)
REFERENCES departments (dep_id) ON DELETE CASCADE ON UPDATE CASCADE
)
ENGINE = INNODB
AUTO_INCREMENT = 6
AVG_ROW_LENGTH = 16384
CHARACTER SET latin1
COLLATE latin1_swedish_ci;
CREATE TABLE std_test (
stdid int(11) NOT NULL,
std_test_id int(11) NOT NULL,
starttime timestamp DEFAULT CURRENT_TIMESTAMP,
endtime timestamp DEFAULT '0000-00-00 00:00:00',
progress enum ('over', 'inprogress') NOT NULL,
PRIMARY KEY (std_test_id),
INDEX stdid (stdid),
INDEX tstid (std_test_id),
CONSTRAINT std_test_ibfk_2 FOREIGN KEY (std_test_id)
REFERENCES test (test_id) ON DELETE RESTRICT ON UPDATE RESTRICT,
CONSTRAINT std_test_ibfk_3 FOREIGN KEY (stdid)
REFERENCES student (std_id) ON DELETE RESTRICT ON UPDATE RESTRICT
)
ENGINE = INNODB
AVG_ROW_LENGTH = 16384
CHARACTER SET latin1
COLLATE latin1_swedish_ci;

Answer 1

untested and shortened, but this is, what i understand, when i read your question
SELECT ....
FROM student s
INNER JOIN test t ON t.depart_id = s.department
LEFT JOIN std_test st ON t.test_id = st.std_test_id
WHERE st.stdid IS NULL
should work now