I need to find the distinct drinkers who have ordered drinks at a pub on VICTORIA AVE. in March 2020.
Here are the tables I am trying to retrieve data from:
x
CREATE TABLE ORDERS( /* Drinkers visit pubs and consumes drinks */
DRINKER VARCHAR(30) NOT NULL, /* Drinker name */
PUB VARCHAR(30) NOT NULL, /* Pub name */
ODATE DATE NOT NULL, /* Order date */
DRINK VARCHAR(30) NOT NULL, /* Drink name */
DRINK_NO DECIMAL(2) NOT NULL, /* A sequence number of a drink */
CONSTRAINT ORDERS_PKEY PRIMARY KEY(DRINKER, PUB, ODATE, DRINK, DRINK_NO),
CONSTRAINT ORDERS_FKEY1 FOREIGN KEY(PUB, DRINK) REFERENCES SERVES(PUB, DRINK),
CONSTRAINT ORDERS_FKEY2 FOREIGN KEY(DRINKER) REFERENCES DRINKERS(DRINKER) );
CREATE TABLE LOCATED( /* Pubs have locations */
PUB VARCHAR(30) NOT NULL, /* Pub name */
STREET VARCHAR(30) NOT NULL, /* Street name */
BLDG_NO DECIMAL(4) NOT NULL, /* Building number */
CONSTRAINT LOCATED_PKEY PRIMARY KEY(PUB) );
Here is my SELECT statement so far:
SELECT DISTINCT DRINKER
FROM ORDERS
WHERE EXISTS (SELECT PUB
FROM LOCATED
WHERE STREET = 'VICTORIA AVE.'
AND ORDERS.ODATE >= STR_TO_DATE('01-MAR-2020','%d-%M-%Y')
AND ORDERS.ODATE <= STR_TO_DATE('01-MAR-2020','%d-%M-%Y'));
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Answer
The subquery needs to be correlated to the main query in its WHERE
clause.
SELECT DISTINCT DRINKER
FROM ORDERS
WHERE EXISTS (SELECT PUB
FROM LOCATED
WHERE LOCATED.PUB = ORDERS.PUB
AND STREET = 'VICTORIA AVE.'
AND ORDERS.ODATE >= STR_TO_DATE('01-MAR-2020','%d-%M-%Y')
AND ORDERS.ODATE <= STR_TO_DATE('31-MAR-2020','%d-%M-%Y'));