DynamoDB: Query Group By (Guide w/ Code Examples)

Rafal Wilinski

Provided by Rafal Wilinski

There is no built-in "group by" functionality in the DynamoDB query method. However, you can retrieve all the data from the table and use JavaScript to group the results by a specific attribute.

For example, you can retrieve all the items from the table, iterate through them and add them to a JavaScript object that is keyed by the attribute you want to group by.

const AWS = require('aws-sdk'); const dynamoDb = new AWS.DynamoDB.DocumentClient(); const params = { TableName: 'tableName', ProjectionExpression: 'attribute1, attribute2, attribute3', }; dynamoDb.scan(params, (error, data) => { if (error) { console.error(error); return; } const groupedData = data.Items.reduce((acc, item) => { const groupKey = item.attribute1; if (!acc[groupKey]) { acc[groupKey] = []; } acc[groupKey].push(item); return acc; }, {}); console.log(groupedData); });

This will allow you to group the data by the attribute attribute1 and you can access the data by their group key.

Please note that, depending on the size of the table and the number of items that need to be grouped, this approach may not be efficient and may consume a large amount of memory.

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