You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ORDER BY prioridad asc,name asc' at line 1

SELECT * FROM hv_course_slides WHERE idpadre= ORDER BY prioridad asc,name asc

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'and varname='avance' LIMIT 0,1' at line 1

SELECT * FROM hv_course_slides_vars WHERE course_module=0 and userid= and varname='avance' LIMIT 0,1

Column 'userid' cannot be null

INSERT INTO hv_course_slides_vars ( COURSE_MODULE, TIME, USERID, SLIDEID, VARNAME, VALUE ) VALUES ( 0, 1576443033, null, 0, 'avance', '0' )