# Keyspaces
<a name="cql.ddl.keyspace"></a>

A *keyspace* groups related tables that are relevant for one or more applications. In terms of a relational database management system (RDBMS), keyspaces are roughly similar to databases, tablespaces, or similar constructs.

**Note**  
In Apache Cassandra, keyspaces determine how data is replicated among multiple storage nodes. However, Amazon Keyspaces is a fully managed service: The details of its storage layer are managed on your behalf. For this reason, keyspaces in Amazon Keyspaces are logical constructs only, and aren't related to the underlying physical storage.

For information about quota limits and constraints for Amazon Keyspaces keyspaces, see [Quotas for Amazon Keyspaces (for Apache Cassandra)](quotas.md).

**Topics**
+ [

## CREATE KEYSPACE
](#cql.ddl.keyspace.create)
+ [

## ALTER KEYSPACE
](#cql.ddl.keyspace.alter)
+ [

## DROP KEYSPACE
](#cql.ddl.keyspace.drop)
+ [

## USE
](#cql.ddl.keyspace.use)

## CREATE KEYSPACE
<a name="cql.ddl.keyspace.create"></a>

Use the `CREATE KEYSPACE` statement to create a new keyspace.

**Syntax**

```
create_keyspace_statement ::= 
    CREATE KEYSPACE [ IF NOT EXISTS ] keyspace_name
    WITH options
```

Where:
+ `keyspace_name` is the name of the keyspace to be created.
+ *options* are one or more of the following:
  + `REPLICATION` – A map that indicates the replication strategy for the keyspace:
    + `SingleRegionStrategy` – For a single-Region keyspace. (Required)
    + `NetworkTopologyStrategy` – Specify at least two AWS Regions. The replication factor for each Region is three. (Optional)
  + `DURABLE_WRITES` – Writes to Amazon Keyspaces are always durable, so this option isn't required. However, if specified, the value must be `true`.
  + `TAGS` – A list of key-value pair tags to be attached to the resource when you create it. (Optional)

**Example**

Create a keyspace as follows.

```
CREATE KEYSPACE my_keyspace
    WITH REPLICATION = {'class': 'SingleRegionStrategy'} and TAGS ={'key1':'val1', 'key2':'val2'} ;
```

To create a multi-Region keyspace, specify `NetworkTopologyStrategy` and include at least two AWS Regions. The replication factor for each Region is three.

```
CREATE KEYSPACE my_keyspace
    WITH REPLICATION = {'class':'NetworkTopologyStrategy', 'us-east-1':'3', 'ap-southeast-1':'3','eu-west-1':'3'};
```

## ALTER KEYSPACE
<a name="cql.ddl.keyspace.alter"></a>

You can use the `ALTER KEYSPACE WITH` statement for the following *options*
+ `REPLICATION` – Use this option to add a new AWS Region replica to a keyspace. You can add a new Region to a single-Region or to a multi-Region keyspace. 
+ `TAGS` – Use this option to add or remove tags from a keyspace.

**Syntax**

```
alter_keyspace_statement ::= 
    ALTER KEYSPACE keyspace_name
    WITH options
```

Where:
+ `keyspace_name` is the name of the keyspace to be altered.
+ *options* are one of the following:
  + `ADD | DROP TAGS` – A list of key-value pair tags to be added or removed from the keyspace. 
  + `REPLICATION` – A map that indicates the replication strategy for the keyspace; 
    + `class`– `NetworkTopologyStrategy` defines the keyspace as a multi-Region keyspace.
    + `region`– Specify one additional AWS Region for this keyspace. The replication factor for each Region is three.
    + `CLIENT_SIDE_TIMESTAMPS` – The default is `DISABLED`. You can only change the status to `ENABLED`.

**Examples**

Alter a keyspace as shown in the following example to add tags.

```
ALTER KEYSPACE my_keyspace ADD TAGS {'key1':'val1', 'key2':'val2'};
```

To add a third Region to a multi-Region keyspace, you can use the following statement.

```
ALTER KEYSPACE my_keyspace
WITH REPLICATION = {
    'class': 'NetworkTopologyStrategy',
    'us-east-1': '3',
    'us-west-2': '3',
    'us-west-1': '3'
} AND CLIENT_SIDE_TIMESTAMPS = {'status': 'ENABLED'};
```

## DROP KEYSPACE
<a name="cql.ddl.keyspace.drop"></a>

Use the `DROP KEYSPACE` statement to remove a keyspace—including all of its contents, such as tables.

**Syntax**

```
drop_keyspace_statement ::= 
    DROP KEYSPACE [ IF EXISTS ] keyspace_name
```

Where:
+ *keyspace\$1name* is the name of the keyspace to be dropped.

**Example**

```
DROP KEYSPACE my_keyspace;
```

## USE
<a name="cql.ddl.keyspace.use"></a>

Use the `USE` statement to define the current keyspace. This allows you to refer to objects bound to a specific keyspace, for example tables and types, without using the fully qualified name that includes the keyspace prefix. 

**Syntax**

```
use_statement ::= 
    USE keyspace_name
```

Where:
+ *keyspace\$1name* is the name of the keyspace to be used.

**Example**

```
USE my_keyspace;
```