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.