I've already tried it with UNIQUE and CHECK but it does not work for me.
If there is a teacher with a subject, I would like you not to put the same subject back to me, because the rest of the code I have makes it repeat.
* * *
for($i=0;$i<count($profesores);$i++){
if($profesores[$i]!="")
{
$Query=$link->prepare ("insert into joom37_docencia_prof_asig (asignatura,profesor) VALUES ('".$asignatura."','".$profesores[$i]."')");
$Query->execute();
}
* *
I would start by creating a UNIQUE key in (asignatura, profesor) .
Once this is done, you can use INSERT IGNORE :
INSERT IGNORE INTO joom37_docencia_prof_asig (asignatura,profesor)
VALUES ('asignatura1','profesor1')
That simply skips the insertion if the new record collides with a single tuple. Also, since we are talking about MySQL you can use the convenience method REPLACE instead of INSERT .
REPLACE INTO joom37_docencia_prof_asig (asignatura,profesor)
VALUES ('asignatura1','profesor1')
But this implies that if the key exists, it will delete the existing row and add another one. If there is a self-incremental ID field, it will change the ID because it will be a new row.
Finally, depending on your use case, you could also use INSERT ... ON DUPLICATE , for example if you want the row containing the single tuple not to be modified, but a field that reflects the last update is updated:
INSERT INTO joom37_docencia_prof_asig (asignatura,profesor)
VALUES ('asignatura1','profesor1')
ON DUPLICATE KEY UPDATE actualizacion = now();
In summary, this is a part of the logic that I would prefer to use with the native tools of the DB to protect the integrity of the data.