How to make a query WHERE NOT EXIST after an INSERT in SQL

To use the where not exists , you need a select . So you need to convert the clause values to select :

INSERT INTO 'pasajeros' ( 'nombre','apellidos','email','password','telefono')
SELECT 'Alexandra','Gonzalez','[email protected]','1234567!','04242344556'
  FROM dual
 WHERE NOT EXISTS ( SELECT * FROM 'transportistas' WHERE 'email' = '[email protected]');

Another way, following the same principle, a little more complicated, but that prevents you from repeating the value for the email in 2 places, is using a derived table:

INSERT INTO 'pasajeros' ( 'nombre','apellidos','email','password','telefono')
SELECT i.nombre, i.apellidos, i.email, i.password, i.telefono
  FROM (SELECT 'Alexandra' as nombre,
               'Gonzalez' as apellidos,
               '[email protected]' as email,
               '1234567!' as password,
               '04242344556' as telefono) i
 WHERE NOT EXISTS ( SELECT * FROM 'transportistas' t WHERE t.'email' = i.email);

Another idea could be with a condition like this:

IF NOT EXISTS 
    (   SELECT  1
        FROM    'transportistas'
        WHERE   'email'= '[email protected]'
    )
    BEGIN
        INSERT 'pasajeros'('nombre','apellidos','email','password','telefono') 
        VALUES ('Alexandra','Gonzalez','[email protected]','1234567!','04242344556') 
    END;

You can also do it with JOIN :

INSERT INTO 'pasajeros' 
          ('nombre','apellidos','email','password','telefono')
   SELECT 'Alexandra','Gonzalez',temp.email,'1234567!','04242344556'
           FROM (SELECT '[email protected]' AS email) temp
           LEFT JOIN transportistas ON transportistas.email = temp.email
           WHERE transportistas.email IS NULL

A temporary table is created with the value of the email and compared with the email column of carriers, if it is NULL, the insertion is made because said email does not exist in carriers.

Dear, I did my work as a researcher and I have found a way in which I could achieve its goal, hopefully it will help. Greetings

INSERT INTO 'pasajeros'('nombre','apellidos','email','password','telefono')
SELECT '[email protected]'
FROM dual
WHERE NOT EXISTS (SELECT 'email' FROM 'pasajeros' WHERE 'email' = '[email protected]')LIMIT 1