Alter the USERS table to change the primary key to Email to ensure uniqueness based on email addresses.
Question
Alter the USERS table to change the primary key to Email to ensure uniqueness based on email addresses.
Solution
To alter the USERS table and change the primary key to Email, you would use the following SQL commands:
Step 1: First, you need to drop the existing primary key. Let's assume the current primary key is UserID.
ALTER TABLE USERS
DROP PRIMARY KEY;
Step 2: Then, you need to add the new primary key, which is Email.
ALTER TABLE USERS
ADD PRIMARY KEY (Email);
Please note that all email values must be unique and not null before setting it as a primary key. If there are duplicate or null values, you will need to handle them before running the above commands.
Similar Questions
Alter the CUSTOMERS table to change the primary key to Email to ensure each customer is uniquely identified by their email address.
Alter the CUSTOMERS table to change the primary key to Email to ensure each customer is uniquely identified by their email address.Drop the primary key from the BOOKINGS table as it is no longer required.
Alter the CUSTOMERS table to change the primary key from CustomerID to Email for better identification of customers.Alter the RESERVATIONS table to allow ReservationTime to be nullable in case some reservations do not have a specific time set.
Charles is developing a travel booking system to manage customers, bookings, and payments. The system needs to handle three main types of data: CUSTOMERS, BOOKINGS, and PAYMENTS. To perform this the user needs to create the following tables with the mentioned constraints: symbol refers to the primary key NN refers to Not NULL After creating the tables, Charles needs to:Alter the CUSTOMERS table to change the primary key to Email to ensure each customer is uniquely identified by their email address.Drop the primary key from the BOOKINGS table as it is no longer required.Note: The user must write only the query to create, alter, and drop the table. The query to display the description of the table is already given.Input format :No console inputOutput format :The output displays the successful table creation status and the structure of all three tablesRefer to the sample output.Sample test cases :Input 1 :Output 1 :Table CUSTOMERS created.Table BOOKINGS created.Table PAYMENTS created.Table CUSTOMERS altered.Table CUSTOMERS altered.Table BOOKINGS altered. Name Null? Type _____________ ___________ ________________ CUSTOMERID NOT NULL NUMBER FIRSTNAME VARCHAR2(100) LASTNAME VARCHAR2(100) EMAIL NOT NULL VARCHAR2(100) Name Null? Type ______________ ___________ ________________ BOOKINGID NOT NULL NUMBER CUSTOMERID NUMBER BOOKINGDATE DATE DESTINATION VARCHAR2(100) Name Null? Type ______________ ___________ _________ PAYMENTID NOT NULL NUMBER BOOKINGID NUMBER AMOUNT NUMBER PAYMENTDATE DATE TABLE_NAME COLUMN_NAME POSITION STATUS _____________ ______________ ___________ __________ CUSTOMERS EMAIL 1 ENABLED 1 row selected.
Select all the correct answersWrite a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest [email protected]@[email protected] is the primary key column for this table.For example, after running your query, the above Person table should have the following rows:[email protected]@example.comNote: Your output is the whole Person table after executing your sql. Use delete statement.Optionsdelete p.* from Person as p, ( select Email, min(Id) as minId from Person where having count(*) > 1) as q where p.Email = q.Email and Id > q.minId;delete p1 from Person as p1, Person as p2where p1.Email = p2.Email and p1.Id > p2.Id;delete p.* from Person as p, ( select Email, min(Id) as minId from Person group by Email having count(*) > 1) as q where p.Email = q.Email and Id > q.minId;delete p1 from Person as p1, Person as p2where p1.Email != p2.Email and p1.Id <= p2.Id;Finish ClearPrev
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