Altering Database Tables and Renaming Columns

Altering a Database Table

• Altering a database table is necessary when corrections or changes are required, such as fixing a typo in a column name, increasing the size of a column, or removing an unnecessary column.
• The ALTER TABLE command is used to modify an existing database table.

Renaming a Column

• The ALTER TABLE command can be used to rename a column in a database table.
• The syntax is ALTER TABLE table_name CHANGE old_column_name new_column_name data_type;.
• Example: ALTER TABLE book CHANGE publisher_name publisher VARCHAR(200);

Adding a New Column

• The ALTER TABLE command can be used to add a new column to a database table.
• The syntax is ALTER TABLE table_name ADD new_column_name data_type;.
• Example: ALTER TABLE book ADD star_rating INT(1);

Removing a Column

• The ALTER TABLE command can be used to remove a column from a database table.
• The syntax is ALTER TABLE table_name DROP COLUMN column_name;.
• Example: ALTER TABLE book DROP COLUMN genre;

Modifying an Existing Column

• The ALTER TABLE command can be used to modify an existing column in a database table.
• The syntax is ALTER TABLE table_name MODIFY COLUMN column_name new_data_type;.
• Example: ALTER TABLE book MODIFY COLUMN retail_price DOUBLE(4, 2);

Using the ALTER TABLE Command

• The ALTER TABLE command can be used to make various changes to a database table, including renaming a column, adding a new column, removing a column, and modifying an existing column.
• The command is used in conjunction with other keywords, such as CHANGE, ADD, DROP, and MODIFY, to specify the type of change to be made.

Altering a Database Table

• Altering a database table is necessary when corrections or changes are required, such as fixing a typo in a column name, increasing the size of a column, or removing an unnecessary column.
• The ALTER TABLE command is used to modify an existing database table.

Renaming a Column

• The ALTER TABLE command can be used to rename a column in a database table.
• Syntax: ALTER TABLE table_name CHANGE old_column_name new_column_name data_type;.
• Example: renaming publisher_name to publisher with a data type of VARCHAR(200).

Adding a New Column

• The ALTER TABLE command can be used to add a new column to a database table.
• Syntax: ALTER TABLE table_name ADD new_column_name data_type;.
• Example: adding a new column star_rating with a data type of INT(1).

Removing a Column

• The ALTER TABLE command can be used to remove a column from a database table.
• Syntax: ALTER TABLE table_name DROP COLUMN column_name;.
• Example: dropping the column genre.

Modifying an Existing Column

• The ALTER TABLE command can be used to modify an existing column in a database table.
• Syntax: ALTER TABLE table_name MODIFY COLUMN column_name new_data_type;.
• Example: modifying the retail_price column to a data type of DOUBLE(4, 2).

Using the ALTER TABLE Command

• The ALTER TABLE command can be used to make various changes to a database table.
• The command is used in conjunction with other keywords, such as CHANGE, ADD, DROP, and MODIFY, to specify the type of change to be made.

Learn about altering database tables, fixing column names, and modifying column sizes with the ALTER TABLE command. Also, understand how to rename a column in a database table.