# SQL

SQL is the primary interface for DeltaStream. Using a simple and familiar SQL interface, you can

* create databases
* run continuous queries
* build materialized views
* and more

DeltaStream also provides SQL extensions that enable you to express streaming concepts that don’t have equivalents in traditional SQL.

## DDL

SQL DDLs are queries that create, delete, or modify database structures. Unlike queries, DDLs do not process data. Examples of useful DDLs include:

* [creating databases](/reference/sql-syntax/ddl/create-database.md)
* [creating streams](/reference/sql-syntax/ddl/create-stream.md)
* [dropping entities](/reference/sql-syntax/ddl/drop-entity.md)
* [updating stores](/reference/sql-syntax/ddl/update-store.md)

DDLs are useful in both the DeltaStream UI and the CLI. However, the UI also provides an interface for many of these DDLs, such as creating [stores](/overview/core-concepts/store.md).

For a full list of SQL DDLs, go to [the DDL page](/reference/sql-syntax/ddl.md) of the [SQL Syntax](/reference/sql-syntax.md) section.

## Query

There are two main types of SQL queries that do process data:

1. [Streaming or continuous queries](/overview/core-concepts/queries.md#_streaming_or_continuous_query)
2. [Materialized view queries](/overview/core-concepts/queries.md#query-on-materialized-views)

See more about both in the [Query](/overview/core-concepts/queries.md) page under [Core Concepts](/overview/core-concepts.md).

When you write streaming queries in the UI, successful queries display in the **Query** tab. Interactive streaming queries and queries on materialized views both print results on the page. Similarly, for the CLI you can list successful streaming queries with the [LIST QUERIES](/reference/sql-syntax/command/list-queries.md) command; interactive streaming queries and queries on materialized views in this case print results directly in the console.

For a full list of SQL queries, go to the [Query](/reference/sql-syntax/query.md) section under [SQL Syntax](/reference/sql-syntax.md).

## Command

SQL commands are actions that do not change database entities and do not process data. Examples of useful commands include:

* listing and describing DeltaStream entities
* inviting users to your organization
* granting privileges
* printing the records in [entities](/overview/core-concepts/store.md#entity)

SQL commands are useful when using the CLI. DeltaStream provides the functionality of these commands through its UI.

For a full list of SQL commands, go to the [Commands](/reference/sql-syntax/command.md) section under [SQL Syntax](/reference/sql-syntax.md).


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