### Database Schema:
CREATE TABLE incidents (
	case_number	TEXT	NOT NULL	PRIMARY KEY,
	date	DATE	NOT NULL,
	location	TEXT	NOT NULL,
	subject_statuses	TEXT	NOT NULL,
	subject_weapon	TEXT	NOT NULL,
	subjects	TEXT	NOT NULL,
	subject_count	INTEGER	NOT NULL,
	officers	TEXT	NOT NULL
);

CREATE TABLE officers (
	case_number	TEXT	NOT NULL,
	race	TEXT	NULL,
	gender	TEXT	NOT NULL,
	last_name	TEXT	NOT NULL,
	first_name	TEXT	NULL,
	full_name	TEXT	NOT NULL,
	foreign key (case_number) references incidents (case_number)
);

CREATE TABLE subjects (
	case_number	TEXT	NOT NULL,
	race	TEXT	NOT NULL,
	gender	TEXT	NOT NULL,
	last_name	TEXT	NOT NULL,
	first_name	TEXT	NULL,
	full_name	TEXT	NOT NULL,
	foreign key (case_number) references incidents (case_number)
);

### User's Query:
Of the black officers, how many of them investigated cases between the years 2010 and 2015?

### Extra Knowledge:
black refers to race = 'B'; between the years 2010 and 2015 refers to date between '2010-01-01' and '2015-12-31'; case refers to case_number
SELECT COUNT(T1.case_number) FROM officers AS T1 INNER JOIN incidents AS T2 ON T2.case_number = T1.case_number WHERE T1.race = 'B' AND T2.date BETWEEN '2010-01-01' AND '2015-12-31'