What is attribute value DynamoDB?
Each attribute value is described as a name-value pair. The name is the data type, and the value is the data itself. For more information, see Data Types in the Amazon DynamoDB Developer Guide.
Can you query in DynamoDB?
Querying is a very powerful operation in DynamoDB. It allows you to select multiple Items that have the same partition (“HASH”) key but different sort (“RANGE”) keys.
How do I get items from DynamoDB table?
Retrieving an item in DynamoDB requires using GetItem, and specifying the table name and item primary key. Be sure to include a complete primary key rather than omitting a portion. For example, omitting the sort key of a composite key.
What is expression attribute values?
Expression attribute values in Amazon DynamoDB are substitutes for the actual values that you want to compare—values that you might not know until runtime. An expression attribute value must begin with a colon ( : ) and be followed by one or more alphanumeric characters.
What is N and S in DynamoDB?
But the only attribute types that are valid for keys are S (string), N (number), and B (binary). Maps are not valid attribute types for either partition or sort keys, so you can’t use them when defining your table or index. DynamoDB is schema-less.
How do I sort DynamoDB query results?
Query results are always sorted by the sort key value. If the data type of the sort key is Number, the results are returned in numeric order; otherwise, the results are returned in order of UTF-8 bytes. By default, the sort order is ascending. To reverse the order, set the ScanIndexForward parameter to false.
What is projection expression in DynamoDB?
Amazon DynamoDB returns all the item attributes by default. To get only some, rather than all of the attributes, use a projection expression. A projection expression is a string that identifies the attributes that you want. To retrieve a single attribute, specify its name.
Can we store list in DynamoDB?
DynamoDB has support for storing complex data types like lists, sets or maps (aka dictionaries/hash tables). This capability allows for flexible usage patterns.
What is KeySchema in DynamoDB?
KeySchema. Specifies the attributes that make up the primary key for a table or an index. The attributes in KeySchema must also be defined in the AttributeDefinitions array. For more information, see Data Model in the Amazon DynamoDB Developer Guide.