Type conversion functions - Simple Log Service - Alibaba Cloud Documentation Center

You can use type conversion functions in a query statement to convert data to the required types.

The following table describes the type conversion functions that are supported by Simple Log Service.

Important If you want to use strings in analytic statements, you must enclose the strings in single quotation marks (''). Strings that are not enclosed or strings that are enclosed in double quotation marks ("") indicate field names or column names. For example, 'status' indicates the status string, and status or "status" indicates the status log field.

Function	Syntax	Description	Supported in SQL	Supported in SPL
cast function	cast(x as type)	Converts the values of the x field to a specified data type. If the cast function fails to convert a value, the query statement that uses this function fails.	√	√
try_cast function	try_cast(x as type)	Converts the values of the x field to a specified data type. If the try_cast function fails to convert a value, the function returns NULL. The query statement that uses this function skips the value and continues to run. Note Logs may contain dirty data. When you query logs, we recommend that you use the try_cast function. This way, conversion failures will not cause your query statement to fail.	√	×
typeof function	typeof(x)	Returns the data type of the x field.	√	×

cast function

The cast function converts the values of the x field to a specified data type. If the cast function fails to convert a value, the query statement that uses this function fails.

Syntax

cast(x as type)

Parameters

Parameter

Description

The value of this parameter is of an arbitrary data type.

type

The value of this parameter is of an SQL data type. Valid values: bigint, varchar, double, boolean, timestamp, decimal, array, and map.

Example: cast(json_parse(key) as array(varchar)).

Each SQL data type maps to a data type that you can use in a Simple Log Service index. For more information, see Appendix: Data type mappings.

Return value type

The data type that is specified by the type parameter.

Examples

SQL

Convert the number 1 to the Boolean type.

Query statement
```
* | select cast(1 as boolean)
```
Query and analysis results

SPL

Convert the number 1 to the Boolean type.

Query statement

* | extend a = cast(1 as boolean)

Query and analysis results

try_cast function

The try_cast function converts the values of the x field to a specified data type. If the try_cast function fails to convert a value, the function returns NULL. The query statement that uses this function skips the value and continues to run.

Syntax

try_cast(x as type)

Parameters

Parameter

Description

The value of this parameter is of an arbitrary data type.

type

The value of this parameter is of an SQL data type. Valid values: bigint, varchar, double, boolean, timestamp, decimal, array, and map.

Example: try_cast(json_parse(key) as map(varchar, varchar)).

Each SQL data type maps to a data type that you can use in a Simple Log Service index. For more information, see Appendix: Data type mappings.

Return value type

The data type that is specified by the type parameter.

Examples

Convert the values of the uid field to the varchar type.

Query statement
```
* | select try_cast(uid as varchar)
```
Query and analysis results

typeof function

The typeof function returns the data type of the x field.

Syntax

typeof(x)

Parameters

Parameter	Description
x	The value of this parameter is of an arbitrary data type.

Return value type

The varchar type.

Examples

Obtain the data type of the request_time field.

Query statement
```
* |SELECT typeof(request_time)
```
Query and analysis results

Appendix: Data type mappings

The following table describes the mappings between the SQL data types and the data types that are supported by Simple Log Service indexes.

Data type supported by Simple Log Service indexes	SQL data type
long	bigint
text	varchar
double	double
json	varchar