> ## Documentation Index
> Fetch the complete documentation index at: https://docs.risingwave.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Deletes and updates

> Similar to traditional databases, RisingWave supports data updates and deletions within tables. Additionally, when data in a table is modified or deleted, any materialized views built on that table will be updated accordingly.

A few details worth noting:

* Data on a table can be updated or deleted, even if the table was created using the `CREATE TABLE ... WITH ...` statement. Of course, since RisingWave does not support transactions, users need to be extra careful with data accuracy;
* A source does not hold any data, so users cannot perform any update or deletion operations on a source.
* Data on a materialized view cannot be directly updated or deleted by users, which aligns with the design of traditional databases.

## Examples

Let's quickly verify how RisingWave handles deletion or modification operations from upstream in materialized views.

First, we create a table `t` and a materialized view `mv`:

```sql theme={null}
CREATE TABLE t (v1 int, v2 int);
insert into t values (1,10), (2,20), (3,30);
CREATE MATERIALIZED VIEW mv as select sum(v1) as v1_sum, sum(v2) as v2_sum from t;
```

Let's check the result in the materialized view:

```sql theme={null}
select * from mv;
```

We get the following result:

```bash theme={null}
 v1_sum | v2_sum
--------+--------
      6 |     60
(1 row)
```

We then add two rows:

```sql theme={null}
insert into t values (4,40), (5,50);
```

Then let's check the result in the materialized view again:

```sql theme={null}
select * from mv;
```

We should get:

```bash theme={null}
 v1_sum | v2_sum
--------+--------
     15 |    150
(1 row)
```

Delete three rows:

```sql theme={null}
delete from t where v1 <= 3;
```

and then check the result in the materialized view:

```sql theme={null}
select * from mv;
```

We should get:

```sql theme={null}
dev=> select * from mv;
 v1_sum | v2_sum
--------+--------
      9 |     90
(1 row)
```