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Type Conversion Function

Last updated: 2024-01-22 10:52:48
    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.
    Function
    Syntax
    Description
    cast
    cast(x as type)
    Parses the data type of x.
    During cast execution, if a value fails to be parsed, the system terminates the entire query and analysis operation.
    try_cast
    try_cast(x as type)
    Parses 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.
    typeof
    typeof(x)
    Returns the data type of x.
    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

    Parameter
    Description
    x
    The parameter value can be of any type.
    type
    SQL data type. Valid values: bigint, varchar, double, boolean, timestamp, decimal, array, or map.
    For the mappings between index and SQL data types, please see Appendix: Data Type Mappings.
    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

    Parameter
    Description
    x
    The parameter value can be of any type.
    type
    SQL data type. Valid values: bigint, varchar, double, boolean, timestamp, decimal, array, or map.
    For the mappings between index and SQL data types, please see Appendix: Data Type Mappings.

    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:
    Index Data Type
    SQL Data Type
    long
    bigint
    text
    varchar
    double
    double
    json
    varchar
    
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