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 ASCII
character code values. For example, a is greater than A, and
a is greater than B. For a list of code values, see http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters.
For Binary, DynamoDB treats each byte of the binary data as unsigned when it compares binary values.
For information on specifying data types in JSON, see JSON Data Format in the Amazon DynamoDB Developer Guide.
A comparator for evaluating attributes in the AttributeValueList. For
example, equals, greater than, less than, etc.
The following comparison operators are available:
EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL | CONTAINS | NOT_CONTAINS |
BEGINS_WITH | IN | BETWEEN
The following are descriptions of each comparison operator.
EQ : Equal. EQ is supported for all data types,
including lists and maps.
AttributeValueList can contain only one AttributeValue
element of type String, Number, Binary, String Set, Number Set, or Binary Set.
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 equal {"NS":["6", "2",
"1"]}.
NE : Not equal. NE is supported for all data types,
including lists and maps.
AttributeValueList can contain only one AttributeValue
of type String, Number, Binary, String Set, Number Set, or Binary Set. If an
item contains an AttributeValue 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 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"]}.
NOT_NULL : The attribute exists. NOT_NULL is supported
for all data types, including lists and maps.
This operator tests for the existence of an attribute, not its data type.
If the data type of attribute "a" is null, and you evaluate it
using NOT_NULL, the result is a Boolean true. This
result is because the attribute "a" exists; its data type is
not relevant to the NOT_NULL comparison operator.
NULL : The attribute does not exist. NULL is supported
for all data types, including lists and maps.
This operator tests for the nonexistence of an attribute, not its data
type. If the data type of attribute "a" is null, and you
evaluate it using NULL, the result is a Boolean
false. This is because the attribute "a"
exists; its data type is not relevant to the NULL comparison
operator.
CONTAINS : Checks for a subsequence, or value in a set.
AttributeValueList can contain only one AttributeValue
element of type String, Number, or Binary (not a set type). If the target
attribute of the comparison is of type String, then the operator checks for a
substring match. If the target attribute of the comparison is of type Binary,
then the operator looks for a subsequence of the target that matches the input.
If the target attribute of the comparison is a set ("SS",
"NS", or "BS"), then the operator evaluates to
true if it finds an exact match with any member of the set.
CONTAINS is supported for lists: When evaluating "a CONTAINS b",
"a" can be a list; however, "b" cannot be a set, a
map, or a list.
NOT_CONTAINS : Checks for absence of a subsequence, or absence of a
value in a set.
AttributeValueList can contain only one AttributeValue
element of type String, Number, or Binary (not a set type). If the target
attribute of the comparison is a String, then the operator checks for the
absence of a substring match. If the target attribute of the comparison is
Binary, then the operator checks for the absence of a subsequence of the target
that matches the input. If the target attribute of the comparison is a set
("SS", "NS", or "BS"), then the
operator evaluates to true if it does not find an exact
match with any member of the set.
NOT_CONTAINS is supported for lists: When evaluating "a NOT CONTAINS
b", "a" can be a list; however, "b" cannot
be a set, a map, or a list.
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).
IN : Checks for matching elements in a list.
AttributeValueList can contain one or more
AttributeValue elements of type String, Number, or Binary.
These attributes are compared against an existing attribute of an item. If any
elements of the input are equal to the item attribute, the expression evaluates
to true.
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"]}
Causes DynamoDB to evaluate the value before attempting a conditional operation:
If Exists is true, DynamoDB will check to
see if that attribute value already exists in the table. If it is found, then
the operation succeeds. If it is not found, the operation fails with a
ConditionCheckFailedException.
If Exists is false, DynamoDB assumes that
the attribute value does not exist in the table. If in fact the value does not
exist, then the assumption is valid and the operation succeeds. If the value is
found, despite the assumption that it does not exist, the operation fails with a
ConditionCheckFailedException.
The default setting for Exists is true. If you supply a
Value all by itself, DynamoDB assumes the attribute exists:
You don't have to set Exists to true, because it is
implied.
DynamoDB returns a ValidationException if:
Exists is true but there is no Value to
check. (You expect a value to exist, but don't specify what that value
is.)
Exists is false but you also provide a
Value. (You cannot expect an attribute to have a value, while
also expecting it not to exist.)
Represents the data for the expected attribute.
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.
Represents a condition to be compared with an attribute value. This condition can be used with
DeleteItem,PutItem, orUpdateItemoperations; if the comparison evaluates to true, the operation succeeds; if not, the operation fails. You can useExpectedAttributeValuein one of two different ways:Use
AttributeValueListto specify one or more values to compare against an attribute. UseComparisonOperatorto specify how you want to perform the comparison. If the comparison evaluates to true, then the conditional operation succeeds.Use
Valueto specify a value that DynamoDB will compare against an attribute. If the values match, thenExpectedAttributeValueevaluates to true and the conditional operation succeeds. Optionally, you can also setExiststo false, indicating that you do not expect to find the attribute value in the table. In this case, the conditional operation succeeds only if the comparison evaluates to false.ValueandExistsare incompatible withAttributeValueListandComparisonOperator. Note that if you use both sets of parameters at once, DynamoDB will return aValidationExceptionexception.