Structured Query Language (SQL)：練習問題

In SQL, which keyword is used in conjunction with SELECT to return only unique values from a column?

Consider the following SQL query:

SELECT ProductName
FROM Products
WHERE Price BETWEEN 10 AND 20;

What is the result of this query?

A database contains two tables: Student (StudentID, Name) and Enrollment (EnrollmentID, StudentID, Course).
Which query correctly retrieves the names of students enrolled in the 'Computer Science' course?

Which SQL command is used to add a new record to a table in a relational database?

Which of the following SQL statements correctly changes the 'City' value to 'London' for all records in the 'Customers' table where the 'ID' is 5?

State the SQL command used to remove all records from a table named LogData where the status is 'expired'.

In SQL, what is the purpose of the LIKE operator, and which wildcard character is used to represent zero or more characters?

In SQL, what is the specific difference between using a primary key and a foreign key when establishing relationships between two tables?

Write a SQL query to retrieve the FirstName and LastName of all students from a table named Students who scored more than 80 marks in a subject called 'Computer Science'. Assume the Students table is linked to a Grades table via StudentID.

A developer needs to define a new table Project using SQL. The table must include:
- ProjectID: An integer that serves as the primary key.
- ProjectName: A string up to 50 characters, which cannot be null.
- StartDate: A date field.
- Budget: A decimal value representing currency.

Write the SQL DDL (Data Definition Language) command to create this table.