# How-to Guides for ksqlDB for Confluent Platform Common ksqlDB tasks include querying structured data, managing connectors, and testing SQL statements—covered in the following guides. - [Query Structured Data](query-structured-data.md#ksqldb-how-to-query-structured-data): Process and query structured data types like structs, maps, and arrays. - [Convert a Changelog to a Table](convert-changelog-to-table.md#ksqldb-how-to-convert-a-changelog-to-a-table): Create a table representing the latest values in a stream. - [Manage Connectors](use-connector-management.md#ksqldb-how-to-use-connector-management): Source and sink data from external systems. - [Update a Running Persistent Query](update-a-running-persistent-query.md#ksqldb-how-to-update-a-running-persistent-query): Change a running persistent query with no downtime. - [Create a User-defined Function](create-a-user-defined-function.md#ksqldb-how-to-create-a-udf): Extend ksqlDB and invoke your custom code. - [Control the Case of Identifiers](control-the-case-of-identifiers.md#ksqldb-how-to-control-case-of-identifiers): Specify the exact capitalization of object names. - [Use a Custom Timestamp Column](use-a-custom-timestamp-column.md#ksqldb-how-to-use-a-custom-timestamp-column): Perform time-based operations using a timestamp in each record. - [Test SQL Statements](test-an-app.md#ksqldb-how-to-test-an-application): Build test suites to assert correct program behavior. - [Variable Substitution](substitute-variables.md#ksqldb-how-to-substitute-variables): Change the content of a query based on variables. - [Use Lambda Functions](use-lambda-functions.md#ksqldb-how-to-use-lambda-functions): Transform columns of structured data without user-defined functions.