What is the ALTER DATABASE statement in MySQL?
The ALTER DATABASE command enables SQL users to change the overall characteristics and structure of any database. These characteristics are stored in the db.opt file in the database directory.
Using ALTER DATABASE
ALTER DATABASE has many features to alter tables in the databases. These include:
- Rename table name
- Add a column
- Change column name
- Delete column
For example, the following table, Student_data, contains the fields Name and Age:
| Name | Age |
|---|---|
| Ali | 19 |
| Michael | 21 |
| Jason | 20 |
Rename table name
Change the name of the table from Student_data to College_data:
ALTER TABLE Student_data;
RENAME College_data;
Add a column
We want to add a column that shows the status of every student:
ALTER TABLE College_data;
ADD Status varchar(255);
| Name | Age | Status |
|---|---|---|
| Ali | 19 | NULL |
| Michael | 21 | NULL |
| Jason | 20 | NULL |
Change column name
Change the name of the column Name to Student_Name:
ALTER TABLE College_data;
CHANGE Name Student_Name;
| Student_Name | Age | Status |
|---|---|---|
| Ali | 19 | NULL |
| Michael | 21 | NULL |
| Jason | 20 | NULL |
Delete column
Delete the column Status from our database:
ALTER TABLE College_data;
DROP COLUMN Status;
| Name | Age |
|---|---|
| Ali | 19 |
| Michael | 21 |
| Jason | 20 |
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