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>