1. Given the name of a movie studio, find the net worth of its president.

Transcription

1 1. Given the name of a movie studio, find the net worth of its president. CREATE FUNCTION GetNetWorth( studio VARCHAR(30) ) RETURNS DECIMAL(9,3) DECLARE worth DECIMAL(9,3); SELECT networth INTO worth FROM STUDIO S JOIN MOVIEEXEC ON S.president=cert WHERE S.name=studio; RETURN worth;

2 2. Given a name and address, return 1 if the person is a movie star but not an executive, 2 if an executive but not a star, 3 if both, and 4 if neither. The following does not work if there are NULL values any comparison with NULL evaluates to UNKNOWN, so 4 will always be returned. CREATE FUNCTION DetermineRole ( name VARCHAR(60), addr VARCHAR(60) ) RETURNS TINYINT IF EXISTS ( SELECT * FROM MOVIESTAR MS WHERE name=ms.name AND addr=ms.address ) THEN IF EXISTS ( SELECT * FROM MOVIEEXEC ME WHERE name=me.name AND addr=me.address ) THEN RETURN 3; ELSE RETURN 1; IF; ELSEIF EXISTS ( SELECT * FROM MOVIEEXEC ME WHERE name=me.name AND addr=me.address ) THEN RETURN 2; ELSE RETURN 4; IF; Adapting the first condition to handle NULL addresses --- IF EXISTS ( SELECT * FROM MOVIESTAR MS WHERE name=ms.name AND ( addr=ms.address OR ( MS.address IS NULL AND addr IS NULL) ) ) THEN Similar adjustments can be made to the other conditions, and also to handle NULL names.

3 3. Given a movie title, year, and star name, insert into STARSIN and add entries in MOVIES and MOVIESTAR as needed. (Fill in unknown values with NULL.) CREATE PROCEDURE InsertStarsIn ( IN movie VARCHAR(60), IN year SMALLINT, IN star VARCHAR(60) ) IF NOT EXISTS ( SELECT * FROM MOVIES M WHERE M.title=movie ) THEN INSERT INTO MOVIES(title,year) VALUES(movie,year); IF; IF NOT EXISTS ( SELECT * FROM MOVIESTAR M WHERE M.name=star ) THEN INSERT INTO VALUES(star,NULL,NULL,NULL); IF; INSERT INTO VALUES(movie,year,star); Note that it is important to add the entries in MOVIES and MOVIESTAR first (if needed), because STARSIN has foreign keys referring to those tables.

4 4. Given a studio name, assign to output parameters the titles of the two longest movies by that studio. Assign NULL if there is (are) no such movie(s). CREATE PROCEDURE GetTwoLongestMovies ( IN studio VARCHAR(60), OUT longest VARCHAR(60), OUT nextlongest VARCHAR(60) ) DECLARE maxlen INT DEFAULT 1; DECLARE nextmaxlen INT DEFAULT 1; DECLARE done BOOLEAN DEFAULT FALSE; DECLARE curtitle VARCHAR(60); DECLARE curlen INT; DECLARE movies CURSOR FOR SELECT M.title,M.length FROM MOVIES M WHERE M.studioName=studio; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; OPEN movies; FETCH movies INTO curtitle,curlen; WHILE NOT done DO IF curlen >= maxlen THEN SET nextmaxlen = maxlen; SET nextlongest = longest; SET maxlen = curlen; SET longest = curtitle; ELSEIF curlen >= nextmaxlen THEN SET nextmaxlen = curlen; SET nextlongest = curtitle; IF; FETCH movies INTO curtitle,curlen; WHILE; CLOSE movies;

5 5. Given a star name, find the title of the earliest movie of more than 120 minutes length in which they appeared. Return NULL if no such movie. CREATE FUNCTION EarliestMovie ( star VARCHAR(40) ) RETURNS VARCHAR(50) DECLARE earliest VARCHAR(50) DEFAULT NULL; SELECT title INTO earliest FROM MOVIES M JOIN STARSIN S ON M.title=S.movieTitle AND M.year=S.movieYear WHERE S.starName=star AND M.year = ( SELECT MIN(M.year) FROM MOVIES M JOIN STARSIN S ON M.title=S.movieTitle AND M.year=S.movieYear WHERE M.length > 120 AND S.starName=star ); RETURN earliest; One could also take advantage of this being a function body to simplify the queries by splitting the two tasks (finding the earliest year and finding the movie that goes with that year) into separate queries. CREATE FUNCTION EarliestMovie ( star VARCHAR(40) ) RETURNS VARCHAR(50) DECLARE minyear YEAR(4) DEFAULT 1; DECLARE earliest VARCHAR(50) DEFAULT NULL; SELECT MIN(M.year) INTO minyear FROM MOVIES M JOIN STARSIN S ON M.title=S.movieTitle AND M.year=S.movieYear WHERE M.length > 120 AND S.starName=star; SELECT title INTO earliest FROM MOVIES M JOIN STARSIN S ON M.title=S.movieTitle AND M.year=S.movieYear WHERE S.starName=star AND M.year=minyear ; RETURN earliest;

6 6. Given an address, find the name of the star with that address if there is exactly one, and NULL otherwise. One strategy: Look before you leap first check the number of stars with the address, then retrieve the desired star if there's only one. CREATE FUNCTION LocateStar2 ( addr VARCHAR(60) ) RETURNS varchar(40) DECLARE star VARCHAR(40) DEFAULT NULL; IF ( SELECT COUNT(*) FROM MOVIESTAR M WHERE M.address=addr ) <> 1 THEN SET star=null; ELSE SELECT M.name INTO star FROM MOVIESTAR M WHERE M.address=addr; IF; RETURN star; Another strategy: Leap before you look try to retrieve the star, and handle the SQL error that results from too many rows. CREATE FUNCTION LocateStar ( addr VARCHAR(60) ) RETURNS VARCHAR(40) DECLARE star VARCHAR(40) DEFAULT NULL; DECLARE CONTINUE HANDLER FOR SQLSTATE '42000' SET star=null; SELECT M.name INTO star FROM MOVIESTAR M WHERE M.address=addr; RETURN star;