10.3.1 Data definition language (DDL)

• What does DDL stand for in SQL?

  Data Definition Language
• DDL in SQL is used to define and manage the structure of a database
• Name three common DDL commands in SQL.

  CREATE, ALTER, DROP
• The CREATE command in DDL is used to define new tables.
• Within tables, DDL allows you to define columns and their data types
• What are primary keys and foreign keys used for in DDL?

  Specifying relationships between tables
• The ALTER command in DDL can be used to modify the structure of existing tables.
• Using the ALTER command, you can add, modify, or delete columns
• What is the purpose of the RENAME command in DDL?

  Rename tables
• The DROP command in DDL is used to delete entire tables.
• DDL is a subset of SQL used to define and manage the structure of a database
• What is the purpose of the CREATE command in DDL?

  Defines new database objects
• What is the purpose of the ALTER command in DDL?

  Modifies existing database objects
• What is the purpose of the DROP command in DDL?

  Removes database objects
• The TRUNCATE command in DDL empties a table while keeping its structure intact.
• The CREATE command in DDL is used to define new database objects, primarily tables
• What is the basic syntax for the CREATE TABLE command in DDL?

  CREATE TABLE TableName ( ColumnName1 DataType1, ColumnName2 DataType2, ... );</latex>
• What does DDL stand for in SQL?

  Data Definition Language
• Key DDL commands include CREATE, ALTER, DROP, and TRUNCATE
• What is the primary function of the CREATE command in DDL?

  Defines new database objects
• The ALTER command in DDL is used to modify existing database objects.
• The TRUNCATE command empties a table while keeping its structure
• Which DDL command modifies existing database objects?

  ALTER
• What is the purpose of the DROP command in DDL?

  Removes database objects
• The TRUNCATE command removes the table structure along with the data.

  False
• What is the basic syntax for the CREATE TABLE command in DDL?

  $CREATE TABLE TableName ( ColumnName1 DataType1, ... );$
• Common data types used in SQL include INT, VARCHAR, DATE, and FLOAT
• What type of data is stored in a column with the INT data type?

  Whole numbers
• What is the purpose of the DATE data type in SQL?

  Stores calendar dates
• Match the primary key feature with its description:

  Purpose ↔️ Uniquely identify each row

  Usage ↔️ Each table must have one

  Values ↔️ Must be unique and non-null
• What is an example of a primary key constraint in SQL?

  $StudentID INT PRIMARY KEY$
• A table can have multiple primary keys.

  False
• Primary key values must be unique and non-null
• What is an example of a foreign key constraint in SQL?

  CourseID INT FOREIGN KEY REFERENCES Courses(CourseID)</latex>
• The DROP COLUMN command is used to delete an existing column in a table.
• What is the syntax to add a column to an existing table using the ALTER TABLE command?

  $ALTER TABLE TableName ADD COLUMN ColumnName DataType;$
• To modify the data type of a column, you use the ALTER TABLE command with the MODIFY COLUMN clause.
• Order the actions performed on a table using the ALTER TABLE command:

  1️⃣ Add a column

  2️⃣ Modify a column

  3️⃣ Drop a column
• What command is used to modify the structure of an existing table in SQL?

  ALTER TABLE
• To add a column in a table, the syntax is ALTER TABLE TableName ADD COLUMN ColumnName DataType;