You can use type conversion functions to convert data types in a query statement.
| Function | Syntax | Description |
|---|---|---|
| cast function | cast(x as type) | Converts the data type of x. If you use the cast function to convert data types and a value fails to be converted, the entire query and analysis process ends. |
| try_cast function | try_cast(x as type) | Converts the data type of x. If you use the try_cast function to convert data types and a value fails to be converted, NULL is returned for the value and the query and analysis process continues.
Note We recommend that you use the try_cast function to query and analyze logs. This prevents the failures of data queries and data analysis due to dirty data.
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cast function
The cast function is used to convert the data type of x. If you use the cast function to convert data types and a value fails to be converted, the entire query and analysis process ends.
Syntax
cast(x as type)Parameters
| Parameter | Description |
|---|---|
| x | The value of this parameter is of an arbitrary data type. |
| type | The SQL data type. Valid values: bigint, varchar, double, timestamp, decimal, array, and map. For information about the mappings between index data types and SQL data types, see Data type mappings. |
Return value type
The return value type is based on the type parameter that you specified.
Examples
Convert the number 1 to a value of the Boolean type.
- Query statement
* | select cast(1 as boolean) - Query and analysis result
try_cast function
The try_cast function is used to convert the data type of x. If you use the try_cast function to convert data types and a value fails to be converted, NULL is returned for the value and the query and analysis process continues.
Syntax
try_cast(x as type)Parameters
| Parameter | Description |
|---|---|
| x | The value of this parameter is of an arbitrary data type. |
| type | The SQL data type. Valid values: bigint, varchar, double, timestamp, decimal, array, and map. For information about the mappings between index data types and SQL data types, see Data type mappings. |
Return value type
The return value type is based on the type parameter that you specified.
Examples
Convert the value of the uid field to a value of the varchar type.
- Query statement
* | select try_cast(uid as varchar) - Query and analysis result
Data type mappings
The following table describes the mappings between index data types and SQL data types.
| Index data type | SQL data type |
|---|---|
| long | bigint |
| text | varchar |
| double | double |
| json | varchar |