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Amazon DynamoDB
Developer Guide (API Version 2012-08-10)

KeyConditions

KeyConditions are the selection criteria for a Query operation. For a query on a table, you can have conditions only on the table primary key attributes. You must provide the partition key name and value as an EQ condition. You can optionally provide a second condition, referring to the sort key.

Note

If you don't provide a sort key condition, all of the items that match the partition key will be retrieved. If a FilterExpression or QueryFilter is present, it will be applied after the items are retrieved.

For a query on an index, you can have conditions only on the index key attributes. You must provide the index partition key name and value as an EQ condition. You can optionally provide a second condition, referring to the index sort key.

Each KeyConditions element consists of an attribute name to compare, along with the following:

  • AttributeValueList - One or more values to evaluate against the supplied attribute. The number of values in the list depends on the ComparisonOperator being used.

    For type Number, value comparisons are numeric.

    String value comparisons for greater than, equals, or less than are based on Unicode with UTF-8 binary encoding. For example, a is greater than A, and a is greater than B.

    For Binary, DynamoDB treats each byte of the binary data as unsigned when it compares binary values.

  • ComparisonOperator - A comparator for evaluating attributes, for example, equals, greater than, less than, and so on.

    For KeyConditions, only the following comparison operators are supported:

    EQ | LE | LT | GE | GT | BEGINS_WITH | BETWEEN

    The following are descriptions of these comparison operators.

    • EQ : Equal.

      AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, {"S":"6"} does not equal {"N":"6"}. Also, {"N":"6"} does not equal {"NS":["6", "2", "1"]}.

    • LE : Less than or equal.

      AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one provided in the request, the value does not match. For example, {"S":"6"} does not equal {"N":"6"}. Also, {"N":"6"} does not compare to {"NS":["6", "2", "1"]}.

    • LT : Less than.

      AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one provided in the request, the value does not match. For example, {"S":"6"} does not equal {"N":"6"}. Also, {"N":"6"} does not compare to {"NS":["6", "2", "1"]}.

    • GE : Greater than or equal.

      AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one provided in the request, the value does not match. For example, {"S":"6"} does not equal {"N":"6"}. Also, {"N":"6"} does not compare to {"NS":["6", "2", "1"]}.

    • GT : Greater than.

      AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one provided in the request, the value does not match. For example, {"S":"6"} does not equal {"N":"6"}. Also, {"N":"6"} does not compare to {"NS":["6", "2", "1"]}.

    • BEGINS_WITH : Checks for a prefix.

      AttributeValueList can contain only one AttributeValue of type String or Binary (not a Number or a set type). The target attribute of the comparison must be of type String or Binary (not a Number or a set type).

    • BETWEEN : Greater than or equal to the first value, and less than or equal to the second value.

      AttributeValueList must contain two AttributeValue elements of the same type, either String, Number, or Binary (not a set type). A target attribute matches if the target value is greater than, or equal to, the first element and less than, or equal to, the second element. If an item contains an AttributeValue element of a different type than the one provided in the request, the value does not match. For example, {"S":"6"} does not compare to {"N":"6"}. Also, {"N":"6"} does not compare to {"NS":["6", "2", "1"]}

Use KeyConditionExpression Instead

Suppose you wanted to retrieve several items with the same partition key from the Music table. You could use a Query request with a KeyConditions parameter, like this:

{
    TableName: "Music", 
    KeyConditions: {
        "SongTitle": {
            ComparisonOperator: "BETWEEN", 
            AttributeValueList: ["A", "M"]
        }, 
        "Artist": {
            ComparisonOperator: "EQ", 
            AttributeValueList: ["No One You Know"]
        }
    }
}

But you could use a KeyConditionExpression instead:

{
    TableName: "Music", 
    KeyConditionExpression: "Artist = :a AND SongTitle BETWEEN :t1 AND :t2", 
    ExpressionAttributeValues: {
        ":a": "No One You Know", 
        ":t1": "A", 
        ":t2": "M"
    }
}