# Database Modification

This section deals with the insertion, updation and deletion of records from the database.

## Insertion

Insert values into a relation using:

```
insert into r values (V1, V2, ..., Vn)
```

We can also insert the results of a select query into a relation (if there are no errors in the result of the query)

```
insert into r select attributes from s where P
```

## Updation

This is used to update existing records.

```
update r set attribute=new_value where P
```

**case** statements can be used for conditional updates, as shown in the example below:

```
update instructor
 set salary = case
               when salary <= 100000 then salary * 1.05
               else salary * 1.03
              end
```

## Deletion

To delete all records, use:

```
delete from r
```

To delete specific records, use:

```
delete from r where P
```


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