W3. SQL Update

Question 1

Q: What is the purpose of the SQL UPDATE statement?

Answer 1

A: To modify existing records in a table.

Question 2

Q: What is the syntax for the UPDATE statement?

Answer 2

UPDATE table_name 
SET column1 = value1, column2 = value2, ... 
WHERE condition;

Question 3

Q: Why is the WHERE clause important in an UPDATE statement?

Answer 3

A: It specifies which records to update; omitting it updates all records in the table.

Question 4

Q: Write an example query to update the contact name and city for the customer with CustomerID = 1.

Answer 4

UPDATE Customers 
SET ContactName = 'Alfred Schmidt', City = 'Frankfurt' 
WHERE CustomerID = 1;

Question 5

Q: How does the WHERE clause affect the number of records updated?

Answer 5

A: It limits the update to records that meet the specified condition(s).

Question 6

Q: Write a query to set the ContactName to “Juan” for all records where the country is “Mexico.”

Answer 6

UPDATE Customers 
SET ContactName = 'Juan' 
WHERE Country = 'Mexico';

Question 7

Q: What happens if you omit the WHERE clause in an UPDATE statement?

Answer 7

A: All records in the table will be updated.

Question 8

Q: Provide an example of an UPDATE statement without a WHERE clause.

Answer 8

UPDATE Customers 
SET ContactName = 'Juan';

(This will update the ContactName for all records in the table.)