# SQL

The SQL language support in eKuiper includes Data Definition Language (DDL), Data Manipulation Language (DML) and Query Language. The SQL support in eKuiper is a subset of ANSI SQL and has some customized extensions.

## SQL in source definition

When create and manage stream or table source, SQL DDL and DML are used as the command payload. Check [streams](../sqls/streams.md) and [tables](../sqls/tables.md) for detail.

## SQL queries in rules

In rules, SQL queries are used to define the business logic. Please check [sql reference](../sqls/overview.md) for detail.