Amazon SimpleDB
Developer Guide (API Version 2009-04-15)
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Select

Description

The Select operation returns a set of Attributes for ItemNames that match the select expression. Select is similar to the standard SQL SELECT statement.

Amazon SimpleDB keeps multiple copies of each domain. When data is written or updated, all copies of the data are updated. However, it takes time for the update to propagate to all storage locations. The data will eventually be consistent, but an immediate read might not show the change. If eventually consistent reads are not acceptable for your application, use ConsistentRead. Although this operation might take longer than a standard read, it always returns the last updated value.

The total size of the response cannot exceed 1 MB. Amazon SimpleDB automatically adjusts the number of items returned per page to enforce this limit. For example, even if you ask to retrieve 2500 items, but each individual item is 10 KB in size, the system returns 100 items and an appropriate next token so you can get the next page of results.

For information on how to construct select expressions, see Using Select to Create Amazon SimpleDB Queries.

Note

Operations that run longer than 5 seconds return a time-out error response or a partial or empty result set. Partial and empty result sets contain a NextToken value, which allows you to continue the operation from where it left off.

Responses larger than one megabyte return a partial result set.

Your application should not excessively retry queries that return QueryTimeout errors. If you receive too many QueryTimeout errors, reduce the complexity of your query expression.

When designing your application, keep in mind that Amazon SimpleDB does not guarantee how attributes are ordered in the returned response.

For information about limits that affect Select, see Limits.

The select operation is case-sensitive.

Request Parameters

Name Description Required
SelectExpression

The expression used to query the domain.

Type: String

Default: None

Yes
ConsistentRead

When set to true, ensures that the most recent data is returned. For more information, see Consistency

Type: Boolean

Default: false

No
NextToken

String that tells Amazon SimpleDB where to start the next list of ItemNames.

Type: String

Default: None

No

Response Elements

Name Description
<Item><Name>... </Name></Item> Item names that match the select expression.
<Attribute> <Name>...</Name> <Value>...</Value> </Attribute> The name and value of the attribute.
NextToken An opaque token indicating that more than MaxNumberOfItems matched, the response size exceeded 1 megabyte, or the execution time exceeded 5 seconds.

Special Errors

Error Description
InvalidParameterValue Value (" + value + ") for parameter MaxNumberOfItems is invalid. MaxNumberOfItems must be between 1 and 2500.
InvalidParameterValue Value (" + value + ") for parameter AttributeName is invalid. Value exceeds maximum length of 1024.
InvalidParameterValue Value (" + value + ") for parameter ConsistentRead is invalid. The ConsistentRead flag should be either true or false.
InvalidNextToken The specified next token is not valid.
InvalidNumberPredicates Too many predicates in the query expression.
InvalidNumberValueTests Too many value tests per predicate in the query expression.
InvalidQueryExpression The specified query expression syntax is not valid.
InvalidSortExpression The sort attribute must be present in at least one of the predicates, and the predicate cannot contain the is null operator.
MissingParameter The request must contain the parameter DomainName.
NoSuchDomain The specified domain does not exist.
QueryTimeout A timeout occurred when attempting to query domain <domain name> with query expression <query expression>. BoxUsage [<box usage value>]"
TooManyRequestedAttributes Too many attributes requested.

Examples

Sample Request

https://sdb.amazonaws.com/
?Action=Select
&AWSAccessKeyId=[valid access key id]
&NextToken=[valid next token]
&SelectExpression=select%20Color%20from%20MyDomain%20where%20Color%20like%20%27Blue%25%27
&ConsistentRead=true
&SignatureVersion=2
&SignatureMethod=HmacSHA256
&Timestamp=2010-01-25T15%3A03%3A09-07%3A00
&Version=2009-04-15
&Signature=[valid signature]
			

Sample Response

<SelectResponse>
  <SelectResult>
    <Item>
      <Name>Item_03</Name>
      <Attribute><Name>Category</Name><Value>Clothes</Value></Attribute>
      <Attribute><Name>Subcategory</Name><Value>Pants</Value></Attribute>
      <Attribute><Name>Name</Name><Value>Sweatpants</Value></Attribute>
      <Attribute><Name>Color</Name><Value>Blue</Value></Attribute>
      <Attribute><Name>Color</Name><Value>Yellow</Value></Attribute>
      <Attribute><Name>Color</Name><Value>Pink</Value></Attribute>
      <Attribute><Name>Size</Name><Value>Large</Value></Attribute>
    </Item>
    <Item>
      <Name>Item_06</Name>
      <Attribute><Name>Category</Name><Value>Motorcycle Parts</Value></Attribute>
      <Attribute><Name>Subcategory</Name><Value>Bodywork</Value></Attribute>
      <Attribute><Name>Name</Name><Value>Fender Eliminator</Value></Attribute>
      <Attribute><Name>Color</Name><Value>Blue</Value></Attribute>
      <Attribute><Name>Make</Name><Value>Yamaha</Value></Attribute>
      <Attribute><Name>Model</Name><Value>R1</Value></Attribute>
    </Item>
  </SelectResult>
  <ResponseMetadata>
    <RequestId>b1e8f1f7-42e9-494c-ad09-2674e557526d</RequestId>
    <BoxUsage>0.0000219907</BoxUsage>
  </ResponseMetadata>
</SelectResponse>