I have a complex sql query which is meant to return all the reviews given by a selected car however, I am only being shown one as seen below as opposed to all of them like in screenshot two.
This is my DDL
:
CREATE TABLE carsType(
carsTypeID INTEGER NOT NULL AUTO_INCREMENT,
carsTypeName VARCHAR(200) NOT NULL,
PRIMARY KEY(carsTypeID)
);
CREATE TABLE carCategoryType(
carCategoryTypeID INTEGER NOT NULL AUTO_INCREMENT,
carCategoryTypeName VARCHAR(200) NOT NULL,
PRIMARY KEY(carCategoryTypeID)
);
CREATE TABLE cars(
carID INTEGER NOT NULL AUTO_INCREMENT,
carsTypeID INTEGER NOT NULL,
carCategoryTypeID INTEGER NOT NULL,
carName VARCHAR(200),
carArea VARCHAR(200),
FOREIGN KEY(carsTypeID) REFERENCES carsType(carsTypeID),
FOREIGN KEY(carCategoryTypeID) REFERENCES carCategoryType(carCategoryTypeID),
PRIMARY KEY(carID)
);
CREATE TABLE carsReview(
carID INTEGER NOT NULL,
carMileage INTEGER NOT NULL,
reviews VARCHAR(200) NOT NULL,
FOREIGN KEY(carID) REFERENCES cars(carID)
);
INSERT INTO carsType VALUES
(NULL, "Hatchback"),
(NULL, "Saloon"),
(NULL, "Sedan");
INSERT INTO carCategoryType VALUES
(NULL, "A"),
(NULL, "B"),
(NULL, "C");
INSERT INTO cars VALUES
(NULL, 1, 1, "Golf", "Germany"),
(NULL, 2, 2, "Ford", "USA"),
(NULL, 2, 2, "Pontiac", "USA");
INSERT INTO carsReview VALUES
(1, 10000, "Good clean car"),
(2, 3000, "Worth it"),
(3, 1000, "Brand spanking new"),
(1, 45000, "She is good"),
(1, 100000, "Gone son"),
(1, 23000, "Looking fine");
This is my complex SQL
query:
SELECT tbl_cars.carID, tbl_cars.carName, tbl_cars.carArea,
(IFNULL(tbl_carsReview.averageMileage, 0.0)) AS finalaverageMileage , tbl_carsReview.reviews, tbl_carsType.carsTypeName,
tbl_carCategoryType.carCategoryTypeName
FROM cars tbl_cars
INNER JOIN carsType tbl_carsType ON
tbl_cars.carsTypeID = tbl_carsType.carsTypeID
INNER JOIN carCategoryType tbl_carCategoryType ON
tbl_cars.carCategoryTypeID = tbl_carCategoryType.carCategoryTypeID
LEFT JOIN (SELECT carsReview.carID, ROUND(AVG(carsReview.reviews),1) AS averageMileage, carsReview.reviews
FROM carsReview) tbl_carsReview
ON tbl_cars.carID = tbl_carsReview.carID
WHERE tbl_cars.carID = 1
This is my sqlfiddle
: http://sqlfiddle.com/#!9/c9a92c/8
You are missing a group by
in the subquery:
SELECT tbl_cars.carID, tbl_cars.carName, tbl_cars.carArea,
(IFNULL(tbl_carsReview.averageMileage, 0.0)) AS finalaverageMileage ,
tbl_carsReview.reviews, tbl_carsType.carsTypeName,
tbl_carCategoryType.carCategoryTypeName
FROM cars tbl_cars INNER JOIN
carsType tbl_carsType
ON tbl_cars.carsTypeID = tbl_carsType.carsTypeID INNER JOIN
carCategoryType tbl_carCategoryType
ON tbl_cars.carCategoryTypeID = tbl_carCategoryType.carCategoryTypeID LEFT JOIN
(SELECT carsReview.carID, ROUND(AVG(carsReview.reviews),1) AS averageMileage, carsReview.reviews
FROM carsReview
GROUP BY carsReview.carID
------^
) tbl_carsReview
ON tbl_cars.carID = tbl_carsReview.carID
WHERE tbl_cars.carID = 1;
EDIT:
If you want the reviews and the average, you need an additional join
:
SELECT tbl_cars.carID, tbl_cars.carName, tbl_cars.carArea,
(IFNULL(tbl_carsReviewAvg.averageMileage, 0.0)) AS finalaverageMileage ,
tbl_carsReview.reviews, tbl_carsType.carsTypeName,
tbl_carCategoryType.carCategoryTypeName
FROM cars tbl_cars INNER JOIN
carsType tbl_carsType
ON tbl_cars.carsTypeID = tbl_carsType.carsTypeID INNER JOIN
carCategoryType tbl_carCategoryType
ON tbl_cars.carCategoryTypeID = tbl_carCategoryType.carCategoryTypeID LEFT JOIN
(SELECT carsReview.carID, ROUND(AVG(carsReview.reviews),1) AS averageMileage, carsReview.reviews
FROM carsReview
GROUP BY carsReview.carID
) tbl_carsReviewAvg
ON tbl_cars.carID = tbl_carsReviewAvg.carID LEFT JOIN
carsReview tbl_carsReview
ON tbl_cars.carID = tbl_carsReview.carID
WHERE tbl_cars.carID = 1;
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.