**THE FOLLOWING IS THE ddl.sql SCHEMA***

create table classroom

(building varchar(15),

room_number varchar(7),

capacity numeric(4,0),

primary key (building, room_number)

);

create table department

(dept_name varchar(20),

building varchar(15),

budget numeric(12,2) check (budget > 0),

primary key (dept_name)

);

create table course

(course_id varchar(8),

title varchar(50),

dept_name varchar(20),

credits numeric(2,0) check (credits > 0),

primary key (course_id),

foreign key (dept_name) references department

on delete set null

);

create table instructor

(ID varchar(5),

name varchar(20) not null,

dept_name varchar(20),

salary numeric(8,2) check (salary > 29000),

primary key (ID),

foreign key (dept_name) references department

on delete set null

);

create table section

(course_id varchar(8),

sec_id varchar(8),

semester varchar(6)

check (semester in ('Fall', 'Winter', 'Spring', 'Summer')),

year numeric(4,0) check (year > 1701 and year

building varchar(15),

room_number varchar(7),

time_slot_id varchar(4),

primary key (course_id, sec_id, semester, year),

foreign key (course_id) references course

on delete cascade,

foreign key (building, room_number) references classroom

on delete set null

);

create table teaches

(ID varchar(5),

course_id varchar(8),

sec_id varchar(8),

semester varchar(6),

year numeric(4,0),

primary key (ID, course_id, sec_id, semester, year),

foreign key (course_id,sec_id, semester, year) references section

on delete cascade,

foreign key (ID) references instructor

on delete cascade

);

create table student

(ID varchar(5),

name varchar(20) not null,

dept_name varchar(20),

tot_cred numeric(3,0) check (tot_cred >= 0),

primary key (ID),

foreign key (dept_name) references department

on delete set null

);

create table takes

(ID varchar(5),

course_id varchar(8),

sec_id varchar(8),

semester varchar(6),

year numeric(4,0),

grade varchar(2),

primary key (ID, course_id, sec_id, semester, year),

foreign key (course_id,sec_id, semester, year) references section

on delete cascade,

foreign key (ID) references student

on delete cascade

);

create table advisor

(s_ID varchar(5),

i_ID varchar(5),

primary key (s_ID),

foreign key (i_ID) references instructor (ID)

on delete set null,

foreign key (s_ID) references student (ID)

on delete cascade

);

create table time_slot

(time_slot_id varchar(4),

day varchar(1),

start_hr numeric(2) check (start_hr >= 0 and start_hr

start_min numeric(2) check (start_min >= 0 and start_min

end_hr numeric(2) check (end_hr >= 0 and end_hr

end_min numeric(2) check (end_min >= 0 and end_min

primary key (time_slot_id, day, start_hr, start_min)

);

create table prereq

(course_id varchar(8),

prereq_id varchar(8),

primary key (course_id, prereq_id),

foreign key (course_id) references course

on delete cascade,

foreign key (prereq_id) references course

);

3. (5 points) (Note: Read the schema of each table in the university database from ddl.sql or using .schema before working on this problem.) Write the following queries in SQL, using the university schema. (You should actually check the queries you write on the database.) (a) names of instructors whose names have at least 5 characters (b) total number of instructors (c) number of instructors whose names are distinct (d) names and salary of instructors by decreasing order of salary and if two instructors have same salary then by ascending order of their names. (e) Find the third highest salary of any instructor