# Data types


The AWS IoT rules engine supports all JSON data types.


**Supported data types**  

| Type | Meaning | 
| --- | --- | 
| Int | A discrete Int. 34 digits maximum. | 
| Decimal |  A `Decimal` with a precision of 34 digits, with a minimum non-zero magnitude of 1E-999 and a maximum magnitude 9.999...E999.  Some functions return `Decimal` values with double precision rather than 34-digit precision.  With SQL V2 (2016-03-23), numeric values that are whole numbers, such as `10.0`, are processed as an `Int` value (`10`) instead of the expected `Decimal` value (`10.0`). To reliably process whole number numeric values as `Decimal` values, use SQL V1 (2015-10-08) for the rule query statement.   | 
| Boolean | True or False. | 
| String | A UTF-8 string. | 
| Array | A series of values that don't have to have the same type. | 
| Object | A JSON value consisting of a key and a value. Keys must be strings. Values can be any type. | 
| Null | Null as defined by JSON. It's an actual value that represents the absence of a value. You can explicitly create a Null value by using the Null keyword in your SQL statement. For example: "SELECT NULL AS n FROM 'topic/subtopic'"  | 
| Undefined |  Not a value. This isn't explicitly representable in JSON except by omitting the value. For example, in the object `{"foo": null}`, the key "foo" returns NULL, but the key "bar" returns `Undefined`. Internally, the SQL language treats `Undefined` as a value, but it isn't representable in JSON, so when serialized to JSON, the results are `Undefined`. <pre> {"foo":null, "bar":undefined} </pre> is serialized to JSON as: <pre> {"foo":null}</pre> Similarly, `Undefined` is converted to an empty string when serialized by itself. Functions called with invalid arguments (for example, wrong types, wrong number of arguments, and so on) return `Undefined`.   | 

## Conversions


The following table lists the results when a value of one type is converted to another type (when a value of the incorrect type is given to a function). For example, if the absolute value function "abs" (which expects an `Int` or `Decimal`) is given a `String`, it attempts to convert the `String` to a `Decimal`, following these rules. In this case, 'abs("-5.123")' is treated as 'abs(-5.123)'.

**Note**  
There are no attempted conversions to `Array`, `Object`, `Null`, or `Undefined`.


**To decimal**  

| Argument type | Result | 
| --- | --- | 
| Int | A Decimal with no decimal point. | 
| Decimal | The source value. | 
| Boolean | Undefined. (You can explicitly use the cast function to transform true = 1.0, false = 0.0.) | 
| String | The SQL engine tries to parse the string as a Decimal. AWS IoT attempts to parse strings matching the regular expression:^-?\$1d\$1(\$1.\$1d\$1)?((?i)E-?\$1d\$1)?\$1. "0", "-1.2", "5E-12" are all examples of strings that are converted automatically to Decimals. | 
| Array | Undefined. | 
| Object | Undefined. | 
| Null | Null. | 
| Undefined | Undefined. | 


**To int**  

| Argument type | Result | 
| --- | --- | 
| Int | The source value. | 
| Decimal | The source value rounded to the nearest Int. | 
| Boolean | Undefined. (You can explicitly use the cast function to transform true = 1.0, false = 0.0.) | 
| String |  The SQL engine tries to parse the string as a Decimal. AWS IoT attempts to parse strings matching the regular expression:^-?\$1d\$1(\$1.\$1d\$1)?((?i)E-?\$1d\$1)?\$1. "0", "-1.2", "5E-12" are all examples of strings that are converted automatically to Decimals. AWS IoT attempts to convert the String to a Decimal, and then truncates the decimal places of that Decimal to make an Int. | 
| Array | Undefined. | 
| Object | Undefined. | 
| Null | Null. | 
| Undefined | Undefined. | 


**To Boolean**  

| Argument type | Result | 
| --- | --- | 
| Int | Undefined. (You can explicitly use the cast function to transform 0 = False, any\$1nonzero\$1value = True.) | 
| Decimal | Undefined. (You can explicitly use the cast function to transform 0 = False, any\$1nonzero\$1value = True.) | 
| Boolean | The original value. | 
| String | "true"=True and "false"=False (case insensitive). Other string values are Undefined. | 
| Array | Undefined. | 
| Object | Undefined. | 
| Null | Undefined. | 
| Undefined | Undefined. | 


**To string**  

| Argument type | Result | 
| --- | --- | 
| Int | A string representation of the Int in standard notation. | 
| Decimal | A string representing the Decimal value, possibly in scientific notation.  | 
| Boolean | "true" or "false". All lowercase. | 
| String | The original value. | 
| Array | The Array serialized to JSON. The resultant string is a comma-separated list, enclosed in square brackets. A String is quoted. A Decimal, Int, Boolean, and Null is not. | 
| Object | The object serialized to JSON. The resultant string is a comma-separated list of key-value pairs and begins and ends with curly braces. A String is quoted. A Decimal, Int, Boolean, and Null is not. | 
| Null | Undefined. | 
| Undefined | Undefined. |