# SQL Exercises/The warehouse

## ExercisesEdit

Select all warehouses.

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SELECT *
FROM Warehouses;

Select all boxes with a value larger than \$150.

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SELECT *
FROM Boxes
WHERE VALUE > 150;

Select all distinct contents in all the boxes.

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SELECT DISTINCT Contents
FROM Boxes;

Select the average value of all the boxes.

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SELECT AVG(VALUE)
FROM Boxes;

Select the warehouse code and the average value of the boxes in each warehouse.

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SELECT Warehouse, AVG(VALUE)
FROM Boxes
GROUP BY Warehouse;

Same as previous exercise, but select only those warehouses where the average value of the boxes is greater than 150.

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SELECT Warehouse, AVG(VALUE)
FROM Boxes
GROUP BY Warehouse
HAVING AVG(VALUE) > 150;

Select the code of each box, along with the name of the city the box is located in.

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SELECT Boxes.Code, Location
FROM Warehouses
INNER JOIN Boxes ON Warehouses.Code = Boxes.Warehouse;

Select the warehouse codes, along with the number of boxes in each warehouse. Optionally, take into account that some warehouses are empty (i.e., the box count should show up as zero, instead of omitting the warehouse from the result).

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/* Not taking into account empty warehouses */
SELECT Warehouse, COUNT(*)
FROM Boxes
GROUP BY Warehouse;

/* Taking into account empty warehouses */
SELECT Warehouses.Code, COUNT(Boxes.Code)
FROM Warehouses LEFT JOIN Boxes
ON Warehouses.Code = Boxes.Warehouse
GROUP BY Warehouses.Code;

Select the codes of all warehouses that are saturated (a warehouse is saturated if the number of boxes in it is larger than the warehouse's capacity).

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SELECT Code
FROM Warehouses
WHERE Capacity <
(
SELECT COUNT(*)
FROM Boxes
WHERE Warehouse = Warehouses.Code
);

Select the codes of all the boxes located in Chicago.

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/* Without subqueries */
SELECT Boxes.Code
FROM Warehouses LEFT JOIN Boxes
ON Warehouses.Code = Boxes.Warehouse
WHERE Location = 'Chicago';

/* With a subquery */
SELECT Code
FROM Boxes
WHERE Warehouse IN
(
SELECT Code
FROM Warehouses
WHERE Location = 'Chicago'
);

Create a new warehouse in New York with a capacity for 3 boxes.

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INSERT
INTO Warehouses
(Location,Capacity)
VALUES ('New York',3);

Create a new box, with code "H5RT", containing "Papers" with a value of \$200, and located in warehouse 2.

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INSERT INTO Boxes
VALUES('H5RT','Papers',200,2);

Reduce the value of all boxes by 15%.

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UPDATE Boxes SET VALUE = VALUE * 0.85;

Apply a 20% value reduction to boxes with a value larger than the average value of all the boxes.

this solution doesn't work with mysql 5.0.67
ERROR 1093 (HY000): You can't specify target table 'Boxes' for update in FROM clause

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UPDATE Boxes SET VALUE = VALUE * 0.80
WHERE VALUE > (SELECT AVG(VALUE) FROM (SELECT * FROM Boxes) AS X);

Remove all boxes with a value lower than \$100.

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DELETE FROM Boxes WHERE VALUE < 100;

Remove all boxes from saturated warehouses.

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DELETE FROM Boxes WHERE Warehouse IN
(
SELECT Code
FROM Warehouses
WHERE Capacity <
(
SELECT COUNT(*)
FROM Boxes
WHERE Warehouse = Warehouses.Code
)
);

## Table creation codeEdit

CREATE TABLE Warehouses (
Code INTEGER PRIMARY KEY NOT NULL,
Location TEXT NOT NULL ,
Capacity INTEGER NOT NULL
);

CREATE TABLE Boxes (
Code TEXT PRIMARY KEY NOT NULL,
Contents TEXT NOT NULL ,
VALUE REAL NOT NULL ,
Warehouse INTEGER NOT NULL
CONSTRAINT fk_Warehouses_Code REFERENCES Warehouses(Code)
);

Click to see MySQL syntax.
CREATE TABLE Warehouses (
Code INTEGER NOT NULL,
Location VARCHAR(255) NOT NULL ,
Capacity INTEGER NOT NULL,
PRIMARY KEY (Code)
);
CREATE TABLE Boxes (
Code VARCHAR(255) NOT NULL,
Contents VARCHAR(255) NOT NULL ,
VALUE REAL NOT NULL ,
Warehouse INTEGER NOT NULL,
PRIMARY KEY (Code),
FOREIGN KEY (Warehouse) REFERENCES Warehouses(Code)
) ENGINE=INNODB;

## Sample datasetEdit

INSERT INTO Warehouses(Code,Location,Capacity) VALUES(1,'Chicago',3);
INSERT INTO Warehouses(Code,Location,Capacity) VALUES(2,'Chicago',4);
INSERT INTO Warehouses(Code,Location,Capacity) VALUES(3,'New York',7);
INSERT INTO Warehouses(Code,Location,Capacity) VALUES(4,'Los Angeles',2);
INSERT INTO Warehouses(Code,Location,Capacity) VALUES(5,'San Francisco',8);

INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('0MN7','Rocks',180,3);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('4H8P','Rocks',250,1);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('4RT3','Scissors',190,4);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('7G3H','Rocks',200,1);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('8JN6','Papers',75,1);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('8Y6U','Papers',50,3);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('9J6F','Papers',175,2);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('LL08','Rocks',140,4);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('P0H6','Scissors',125,1);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('P2T6','Scissors',150,2);
INSERT INTO Boxes(Code,Contents,VALUE,Warehouse) VALUES('TU55','Papers',90,5);
Last modified on 20 August 2012, at 19:58