# Database Connector operations, parameters and transactions

*MuleSoft Developer Study Guide · Using Connectors · Last updated October 28, 2026 · https://www.certifyforce.com/study-guide/mulesoft-developer/using-connectors/database-connector-operations-parameters-and-transactions*

Which Database Connector operation returns what (Select, Query Single, Insert, Bulk Insert), how input parameters and dynamic queries keep SQL safe, how to connect with Generic Connection and a pooling profile, and how operations join a transaction.

- Certification: Salesforce MuleSoft Developer
- Exam section: Using Connectors
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-developer

**Official exam objective:**

> Apply correct processors/syntax to connect to databases, and predict outcomes.

## What the exam expects

- Write a Select whose WHERE values come from input parameters, and build a dynamic table name with DataWeave interpolation without giving up the parameters.
- Predict what Select, Query Single, Insert and Bulk Insert put in the payload, including generated keys and the case where a later processor needs the original payload.
- Choose a connection type (Generic Connection plus a JDBC driver for an unsupported database) and tune the pooling profile.
- Predict what each `transactionalAction` value does on a Database operation, how operations join a Try scope transaction, and why a streamed Select fails after its transaction closes.
- Key terms: **input parameters** (a map bound on the JDBC prepared statement, referenced as `:name`); **dynamic query** (SQL text built with a `#[ ]` string and `$( )` interpolation); **Statement Result** (Insert/Update output with affected rows and generated keys); **pooling profile** (settings for the connection pool); **transactional action** (how an operation relates to an active transaction).

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Input parameters | Map bound on the JDBC prepared statement; referenced as `:name` in the SQL | [Query a Database Examples](https://docs.mulesoft.com/db-connector/latest/database-connector-select) |
| Select output | Array of Object, streamed automatically | [Database Connector Reference 1.16](https://docs.mulesoft.com/db-connector/latest/database-documentation) |
| Query Single output | Object; first record only when several match; no streaming | [Database Connector Reference 1.16](https://docs.mulesoft.com/db-connector/latest/database-documentation) |
| Insert / Update output | Statement Result (Affected Rows, Generated Keys) | [Database Connector Reference 1.16](https://docs.mulesoft.com/db-connector/latest/database-documentation) |
| Auto Generate Keys | Default `false` | [Database Connector Reference 1.16](https://docs.mulesoft.com/db-connector/latest/database-documentation) |
| Keep records after Bulk Insert | Store its result in a target variable | [Enrich Data with Target Variables](https://docs.mulesoft.com/mule-runtime/latest/target-variables) |
| Unsupported database | Generic Connection with URL and Driver class name | [Configure a Database Connection](https://docs.mulesoft.com/db-connector/latest/database-connector-connection) |
| Test Connection On Checkout | Default true; deselect it to improve pooled performance | [Configure a Database Connection](https://docs.mulesoft.com/db-connector/latest/database-connector-connection) |
| Max Wait | Default 0, which means wait indefinitely | [Database Connector Reference 1.16](https://docs.mulesoft.com/db-connector/latest/database-documentation) |
| Default transactional action | `JOIN_IF_POSSIBLE`; `ALWAYS_JOIN` errors with no transaction | [Configure Database Transactions Example](https://docs.mulesoft.com/db-connector/latest/database-connector-transactions) |

## Check yourself

- Why does Query Single not exhaust a small connection pool?
- What happens to rows beyond Max Rows on a Select?
- When does a Max Wait of `0` matter?
- What does Acquire Increment control?

## Sources

- [Query a Database Examples](https://docs.mulesoft.com/db-connector/latest/database-connector-select)
- [Database Connector Reference 1.16](https://docs.mulesoft.com/db-connector/latest/database-documentation)
- [Query a Single Record from a Database Example](https://docs.mulesoft.com/db-connector/latest/database-connector-query-single)
- [Configure a Database Connection](https://docs.mulesoft.com/db-connector/latest/database-connector-connection)
- [Configure Database Transactions Example](https://docs.mulesoft.com/db-connector/latest/database-connector-transactions)
- [Enrich Data with Target Variables](https://docs.mulesoft.com/mule-runtime/latest/target-variables)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 11 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Developer pack (USD $19): https://www.certifyforce.com/practice-exams