Database schema:

CREATE TABLE cites (
	cited_paper_id TEXT NOT NULL -- example: ['100157', '100598'],
	citing_paper_id TEXT NOT NULL -- example: ['364207', '100157'],
	PRIMARY KEY (cited_paper_id, citing_paper_id)
)


CREATE TABLE content (
	paper_id TEXT NOT NULL -- example: ['100157', '100598'],
	word_cited_id TEXT NOT NULL -- example: ['word1163', 'word1509'],
	PRIMARY KEY (paper_id, word_cited_id), 
	CONSTRAINT fk_content_paper FOREIGN KEY(paper_id) REFERENCES paper (paper_id)
)


CREATE TABLE paper (
	paper_id TEXT NOT NULL -- example: ['100157', '100598'],
	class_label TEXT NOT NULL -- example: ['IR', 'Agents'],
	PRIMARY KEY (paper_id)
)

Question: Calculate the percentage of words used in Agents class label.
Evidence: percentage = (divide(count(word_cited_id where class_label = 'Agents')), (count(word_cited_id)))*100;

SQL:
SELECT CAST(COUNT(DISTINCT CASE WHEN T1.class_label = 'Agents' THEN T2.word_cited_id ELSE NULL END) AS REAL) * 100 / COUNT(DISTINCT T2.word_cited_id) FROM paper AS T1 INNER JOIN content AS T2 ON T1.paper_id = T2.paper_id