# Use a crawler to add a table
<a name="schema-crawlers"></a>

Amazon Glue crawlers help discover the schema for datasets and register them as tables in the Amazon Glue Data Catalog. The crawlers go through your data and determine the schema. In addition, the crawler can detect and register partitions. For more information, see [Defining crawlers](https://docs.amazonaws.cn/glue/latest/dg/add-crawler.html) in the *Amazon Glue Developer Guide*. Tables from data that were successfully crawled can be queried from Athena.

**Note**  
Athena does not recognize [exclude patterns](https://docs.amazonaws.cn/glue/latest/dg/define-crawler.html#crawler-data-stores-exclude) that you specify for an Amazon Glue crawler. For example, if you have an Amazon S3 bucket that contains both `.csv` and `.json` files and you exclude the `.json` files from the crawler, Athena queries both groups of files. To avoid this, place the files that you want to exclude in a different location. 

## Create an Amazon Glue crawler
<a name="data-sources-glue-crawler-setup"></a>

You can create a crawler by starting in the Athena console and then using the Amazon Glue console in an integrated way. When you create the crawler, you specify a data location in Amazon S3 to crawl.

**To create a crawler in Amazon Glue starting from the Athena console**

1. Open the Athena console at [https://console.amazonaws.cn/athena/](https://console.amazonaws.cn/athena/home).

1. In the query editor, next to **Tables and views**, choose **Create**, and then choose **Amazon Glue crawler**. 

1. On the **Amazon Glue** console **Add crawler** page, follow the steps to create a crawler. For more information, see [Using Amazon Glue Crawlers](#schema-crawlers) in this guide and [Populating the Amazon Glue Data Catalog](https://docs.amazonaws.cn/glue/latest/dg/populate-catalog-methods.html) in the *Amazon Glue Developer Guide*.

**Note**  
Athena does not recognize [exclude patterns](https://docs.amazonaws.cn/glue/latest/dg/define-crawler.html#crawler-data-stores-exclude) that you specify for an Amazon Glue crawler. For example, if you have an Amazon S3 bucket that contains both `.csv` and `.json` files and you exclude the `.json` files from the crawler, Athena queries both groups of files. To avoid this, place the files that you want to exclude in a different location.

After a crawl, the Amazon Glue crawler automatically assigns certain table metadata to help make it compatible with other external technologies like Apache Hive, Presto, and Spark. Occasionally, the crawler may incorrectly assign metadata properties. Manually correct the properties in Amazon Glue before querying the table using Athena. For more information, see [Viewing and editing table details](https://docs.amazonaws.cn/glue/latest/dg/console-tables.html#console-tables-details) in the *Amazon Glue Developer Guide*.

Amazon Glue may mis-assign metadata when a CSV file has quotes around each data field, getting the `serializationLib` property wrong. For more information, see [Handling CSV data enclosed in quotes](schema-csv.md#schema-csv-quotes).