### Database Schema:
CREATE TABLE connected (
	atom_id	TEXT	NOT NULL	PRIMARY KEY,
	atom_id2	TEXT	NOT NULL	PRIMARY KEY,
	bond_id	TEXT	NULL	DEFAULT NULL,
	foreign key (atom_id2) references atom (atom_id),
	foreign key (atom_id) references atom (atom_id),
	foreign key (bond_id) references bond (bond_id)
);

CREATE TABLE atom (
	atom_id	TEXT	NOT NULL	PRIMARY KEY,
	molecule_id	TEXT	NULL	DEFAULT NULL,
	element	TEXT	NULL	DEFAULT NULL,
	foreign key (molecule_id) references molecule (molecule_id)
);

CREATE TABLE bond (
	bond_id	TEXT	NOT NULL	PRIMARY KEY,
	molecule_id	TEXT	NULL	DEFAULT NULL,
	bond_type	TEXT	NULL	DEFAULT NULL,
	foreign key (molecule_id) references molecule (molecule_id)
);

CREATE TABLE molecule (
	molecule_id	TEXT	NOT NULL	PRIMARY KEY,
	label	TEXT	NULL	DEFAULT NULL
);

### User's Query:
What is the ratio of Hydrogen elements in molecule ID TR006? List the ratio with its label.

### Extra Knowledge:
hydrogen refers to element = 'h'; ratio = DIVIDE(SUM(element = 'h'), count(element)) where molecule_id = 'TR006' ; label = '+' mean molecules are carcinogenic; label = '-' means molecules are non-carcinogenic
WITH SubQuery AS (SELECT DISTINCT T1.atom_id, T1.element, T1.molecule_id, T2.label FROM atom AS T1 INNER JOIN molecule AS T2 ON T1.molecule_id = T2.molecule_id WHERE T2.molecule_id = 'TR006') SELECT CAST(COUNT(CASE WHEN element = 'h' THEN atom_id ELSE NULL END) AS REAL) / (CASE WHEN COUNT(atom_id) = 0 THEN NULL ELSE COUNT(atom_id) END) AS ratio, label FROM SubQuery GROUP BY label