How to Update Item in DynamoDB: Syntax and Example

To update an item in DynamoDB, use the UpdateItem operation with a key to identify the item and an UpdateExpression to specify attribute changes. You can add, modify, or remove attributes atomically without replacing the entire item.

Syntax

The UpdateItem operation requires specifying the TableName, the Key of the item to update, and an UpdateExpression that defines the changes. You can also use ExpressionAttributeValues to safely pass values and ReturnValues to get the updated item back.

• TableName: The name of your DynamoDB table.
• Key: The primary key of the item you want to update.
• UpdateExpression: A string that describes the attributes to update.
• ExpressionAttributeValues: Values used in the update expression.
• ReturnValues: What to return after update (e.g., ALL_NEW returns the updated item).

json

{
  "TableName": "YourTableName",
  "Key": { "PrimaryKeyName": { "S": "PrimaryKeyValue" } },
  "UpdateExpression": "set AttributeName = :value",
  "ExpressionAttributeValues": { ":value": { "S": "NewValue" } },
  "ReturnValues": "ALL_NEW"
}

Example

This example updates the "Status" attribute of an item with primary key "OrderId" in the "Orders" table to "Shipped" and returns the updated item.

javascript

const { DynamoDBClient, UpdateItemCommand } = require("@aws-sdk/client-dynamodb");

const client = new DynamoDBClient({ region: "us-east-1" });

async function updateOrderStatus() {
  const params = {
    TableName: "Orders",
    Key: {
      "OrderId": { S: "12345" }
    },
    UpdateExpression: "set #st = :s",
    ExpressionAttributeNames: { "#st": "Status" },
    ExpressionAttributeValues: {
      ":s": { S: "Shipped" }
    },
    ReturnValues: "ALL_NEW"
  };

  try {
    const command = new UpdateItemCommand(params);
    const response = await client.send(command);
    console.log("Updated item:", response.Attributes);
  } catch (error) {
    console.error(error);
  }
}

updateOrderStatus();

Output

Updated item: { OrderId: { S: '12345' }, Status: { S: 'Shipped' } }

Common Pitfalls

• Not specifying the correct Key will cause the update to fail because DynamoDB won't find the item.
• Forgetting to use ExpressionAttributeNames when your attribute names are reserved words or contain special characters.
• Using UpdateExpression syntax incorrectly, such as missing the set keyword or wrong placeholders.
• Not handling conditional updates properly can overwrite data unintentionally.

json

/* Wrong: Missing 'set' keyword in UpdateExpression */
UpdateExpression: "Status = :s",

/* Right: Correct UpdateExpression syntax */
UpdateExpression: "set Status = :s"

Quick Reference

Parameter	Description
TableName	Name of the DynamoDB table
Key	Primary key of the item to update
UpdateExpression	Expression defining attribute updates
ExpressionAttributeValues	Values used in the update expression
ExpressionAttributeNames	Optional names for attributes (for reserved words)
ReturnValues	What to return after update (e.g., ALL_NEW)

Key Takeaways

Use UpdateItem with a Key and UpdateExpression to change item attributes in DynamoDB.

Always use ExpressionAttributeNames for reserved words and ExpressionAttributeValues for safe value substitution.

ReturnValues set to ALL_NEW returns the updated item after the operation.

Check your UpdateExpression syntax carefully to avoid errors.

Ensure the Key matches the item you want to update exactly.