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

# sql

> Transform data using DuckDB SQL queries

Transform data using SQL queries. SQL steps read from tables produced by previous steps and produce new output tables:

```typescript theme={null}
{
  sql: `
    SELECT
      o.id,
      o.order_number,
      CAST(o.total_price AS DOUBLE) AS revenue,
      o.created_at,
      c.email AS customer_email
    FROM raw_orders o
    LEFT JOIN raw_customers c ON o.customer_id = c.id
    WHERE o.created_at >= '{{var.startDate}}'
  `,
  outputTable: "enriched_orders",
  outputSchema: {
    id: "VARCHAR",
    order_number: "INTEGER",
    revenue: "DOUBLE",
    created_at: "VARCHAR",
    customer_email: "VARCHAR",
  },
}
```

| Field          | Required | Description                                        |
| -------------- | -------- | -------------------------------------------------- |
| `sql`          | Yes      | DuckDB SQL query (SELECT statements and CTEs only) |
| `outputTable`  | Yes      | Name of the table this step produces               |
| `outputSchema` | Yes      | Column names and types for the result output table |

## SQL safety

* Only `SELECT` statements and CTEs (`WITH ... AS`) are allowed
* Mutations (i.e. `INSERT`, `UPDATE`, `DELETE`) are blocked
* Variables are parameterized to prevent SQL injection
* Tables are isolated per job — one job cannot access the results of any other job

## Validation

| Check                                                        |
| ------------------------------------------------------------ |
| Referenced tables exist in previous steps                    |
| SQL syntax is valid                                          |
| Column references are validated against source table schemas |