tencent cloud

This document introduces the basic syntax and examples of type conversion functions.

If you need to distinguish more detailed data types when querying and analyzing data, you can use type conversion functions for data type conversion in query and analysis statements.

Note：

When dirty data may exist in logs, you are advised to use the try_cast function to avoid query and analysis failures caused by dirty data.

Function cast

The cast function is used to parse the data type of x. During cast execution, if a value fails to be parsed, the system terminates the entire query and analysis operation.

Syntax

cast(x as type)

Parameter description

If type is timestamp, x must be a timestamp in milliseconds (such as 1597807109000) or a time string in the ISO 8601 time format (such as 2019-12-25T16:17:01+08:00).

Return value type

The return value type is determined by the type parameter.

Example

1. Parse the numeric value 0.01 into a BIGINT value:

   * | select cast(0.01 as bigint)
   

2. Convert the CLS log collection time __TIMESTAMP__ to TIMESTAMP.

   * | select cast(__TIMESTAMP__ as timestamp)
   

Function try_cast

The try_cast function is used to parse the data type of x. During try_cast execution, if a value fails to be parsed, the system returns NULL and continues processing by skipping the value.

Syntax

try_cast(x as type)

Parameter description

Return value type

The return value type is determined by the type parameter.

Example

Parse the remote_user field value into a VARCHAR value:

* | select try_cast(remote_user as varchar)

Appendix: Data Type Mappings

The mappings between index and SQL data types are as follows: