### Database Schema:
CREATE TABLE prof (
	prof_id	INTEGER	NULL	PRIMARY KEY,
	gender	TEXT	NULL,
	first_name	TEXT	NULL,
	last_name	TEXT	NULL,
	email	TEXT	NULL,
	popularity	INTEGER	NULL,
	teachingability	INTEGER	NULL,
	graduate_from	TEXT	NULL
);

CREATE TABLE RA (
	student_id	INTEGER	NULL	PRIMARY KEY,
	capability	INTEGER	NULL,
	prof_id	INTEGER	NULL	PRIMARY KEY,
	salary	TEXT	NULL,
	foreign key (student_id) references student (student_id),
	foreign key (prof_id) references prof (prof_id)
);

CREATE TABLE student (
	student_id	INTEGER	NULL	PRIMARY KEY,
	f_name	TEXT	NULL,
	l_name	TEXT	NULL,
	phone_number	TEXT	NULL,
	email	TEXT	NULL,
	intelligence	INTEGER	NULL,
	gpa	REAL	NULL,
	type	TEXT	NULL
);

CREATE TABLE registration (
	course_id	INTEGER	NULL	PRIMARY KEY,
	student_id	INTEGER	NULL	PRIMARY KEY,
	grade	TEXT	NULL,
	sat	INTEGER	NULL,
	foreign key (student_id) references student (student_id),
	foreign key (course_id) references course (course_id)
);

CREATE TABLE course (
	course_id	INTEGER	NULL	PRIMARY KEY,
	name	TEXT	NULL,
	credit	INTEGER	NULL,
	diff	INTEGER	NULL
);

### User's Query:
What is the percentage of Professor Ogdon Zywicki's research assistants are taught postgraduate students?

### Extra Knowledge:
research assistant refers to the student who serves for research where the abbreviation is RA; taught postgraduate student refers to type = 'TPG'; DIVIDE(COUNT(student_id where type = 'TPG' and first_name = 'Ogdon', last_name = 'Zywicki'), COUNT(first_name = 'Ogdon', last_name = 'Zywicki')) as percentage;
SELECT CAST(SUM(CASE WHEN T3.type = 'TPG' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.student_id) FROM RA AS T1 INNER JOIN prof AS T2 ON T1.prof_id = T2.prof_id INNER JOIN student AS T3 ON T1.student_id = T3.student_id WHERE T2.first_name = 'Ogdon' AND T2.last_name = 'Zywicki'