Redshift unload12/8/2023 ![]() ![]() Use the MAXFILESIZE option to dictate file size, with 5 MB being the smallest, and 6.2 GB the largest. Options for outputting to S3 include file size, force one file, file name prefix, and more. I use the double quote escape syntax, with '''' for each quote: UNLOAD ('select * from shows where title=''''AGT''''') to 's3://redshift-output/shows.csv' The UNLOAD command takes a string for your query, so if you need quotes '' in it, select * from shows where title=‘AGT’ for example, you’ll need to escape the quotes. If your query is small, some of the output files will be empty. Depending on how many slices your cluster has, a file will be written for each slice. How to safely unload/copy a table in RedShift Ask Question Asked 8 years, 10 months ago Modified 6 months ago Viewed 17k times Part of AWS Collective 13 In RedShift, it is convenient to use unload/copy to move data to S3 and load back to redshift, but I feel it is hard to choose the delimiter each time. By default UNLOAD will write files in the format 0000_part_00, 0001_part_00, etc. For example, we’ll use CSV to export data in CSV format as an option.Įxample statement: UNLOAD ('select * from shows') to 's3://redshift-output/shows/'Īuthorization 'aws_iam_role=arn:aws:iam:::role/'Īfter running the UNLOAD statement in the query editor, you can find your results saved in S3 with the path s3://redshift-output/shows/. To do so we’l need to define an S3 location, an IAM role for permissions, and any options to include. ![]() We can use that select query with an UNLOAD command. In this example we’ll have a single table, shows with a list of shows with show titles and descriptions: select * from shows You would want to use two single quotes to enclose the value. In this case, you must use the ESCAPE option with the UNLOAD statement. To use S3 as a data source for Redshift and to export data, first write the query to export the data. When you UNLOAD using a delimiter, your data can include that delimiter or any of the characters listed in the ESCAPE option description. For more information about creating IAM roles for Redshift see AWS docs here: Redshift and IAM Roles Exporting Data PrerequisitesĪccess to an AWS Redshift cluster, access to the query editor, and an IAM role with permissions to write to the S3 location. With the UNLOAD command, we can save files in CSV or JSON format directly to S3. With Redshift we can select data and send to data sources available to us in AWS Cloud.
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