Activities

You can use Database Studio to enter and execute SQL statements. More information: Working with SQL Statements: Overview

SELECT reservation.rno, customer.name, reservation.arrival, reservation.departure

  FROM hotel.customer, hotel.reservation

    WHERE customer.name = 'Porter'

AND customer.cno = reservation.cno

Displaying whether and when a reservation was made for the customer Porter

Result

The link between the two tables is established on the basis of the customer number, that is, only those rows that contain the name Porter and in which the customer numbers are identical are selected. =, <, <=, >, >= and <> are possible operators in the WHERE clause.

The overall result row comprises the desired columns in the relevant table. If columns in two different tables have the same name, the table name must be specified in the statement before the column name; the two names are then linked by a period (.).

SELECT customer.name, reservation.rno, hotel.name hotel_name

  FROM hotel.customer, hotel.reservation, hotel.hotel

    WHERE customer.name = 'Porter'

    AND customer.cno = reservation.cno

    AND reservation.hno = hotel.hno

Displaying all the hotels in which the customer Porter has made a reservation. For this purpose, the customer, reservation and hotel tables must be concatenated.

Result

Another example for a join table:

SELECT hotel.name hotel_name, city.zip, city.name city_name

  FROM hotel.hotel, hotel.city

    WHERE city.state = 'CA' AND city.zip=hotel.zip

Displaying the cities in the state of CA for which hotels are specified in the hotel table

Result