CAST

将输入转换为指定的类型。例如，cast (input as BIGINT) 将输入转换为 BIGINT 值。

从 v2.4 版本起，StarRocks 支持转换为 ARRAY 类型。

语法

cast (input as type)

参数

input：要转换的数据。type：目标数据类型。

返回值

返回一个数据类型与 type 相同的值。

示例

示例 1：常见数据转换

    select cast('9.5' as DECIMAL(10,2));
    +--------------------------------+
    | CAST('9.5' AS DECIMAL64(10,2)) |
    +--------------------------------+
    |                           9.50 |
    +--------------------------------+
    
    select cast(NULL AS INT);
    +-------------------+
    | CAST(NULL AS INT) |
    +-------------------+
    |              NULL |
    +-------------------+
    
    select cast(true AS BOOLEAN);
    +-----------------------+
    | CAST(TRUE AS BOOLEAN) |
    +-----------------------+
    |                     1 |
    +-----------------------+
    
    select cast (1 as BIGINT);
    +-------------------+
    | CAST(1 AS BIGINT) |
    +-------------------+
    |                 1 |
    +-------------------+

示例 2：将输入转换为 ARRAY。

    -- Convert string to ARRAY<ANY>.

    select cast('[1,2,3]' as array<int>);
    +-------------------------------+
    | CAST('[1,2,3]' AS ARRAY<INT>) |
    +-------------------------------+
    | [1,2,3]                       |
    +-------------------------------+

    select cast('[1,2,3]' as array<bigint>);
    +----------------------------------+
    | CAST('[1,2,3]' AS ARRAY<BIGINT>) |
    +----------------------------------+
    | [1,2,3]                          |
    +----------------------------------+

    select cast('[1,2,3]' as array<string>);
    +------------------------------------------+
    | CAST('[1,2,3]' AS ARRAY<VARCHAR(65533)>) |
    +------------------------------------------+
    | ["1","2","3"]                            |
    +------------------------------------------+

    select cast('["a", "b", "c"]' as array<string>);
    +--------------------------------------------------+
    | CAST('["a", "b", "c"]' AS ARRAY<VARCHAR(65533)>) |
    +--------------------------------------------------+
    | ["a","b","c"]                                    |
    +--------------------------------------------------+

    -- Convert JSON array to ARRAY<ANY>.

    select cast(parse_json('[{"a":1}, {"a": 2}]')  as array<json>);
    +----------------------------------------------------------+
    | CAST((parse_json('[{"a":1}, {"a": 2}]')) AS ARRAY<JSON>) |
    +----------------------------------------------------------+
    | ['{"a": 1}','{"a": 2}']                                  |
    +----------------------------------------------------------+
    
    select cast(parse_json('[1, 2, 3]')  as array<int>);
    +-----------------------------------------------+
    | CAST((parse_json('[1, 2, 3]')) AS ARRAY<INT>) |
    +-----------------------------------------------+
    | [1,2,3]                                       |
    +-----------------------------------------------+
    
    select cast(parse_json('["1","2","3"]') as array<string>);
    +--------------------------------------------------------------+
    | CAST((parse_json('["1","2","3"]')) AS ARRAY<VARCHAR(65533)>) |
    +--------------------------------------------------------------+
    | ["1","2","3"]                                                |
    +--------------------------------------------------------------+

示例 3：加载期间转换数据。

    curl --location-trusted -u <username>:<password> -T ~/user_data/bigint \
        -H "columns: tmp_k1, k1=cast(tmp_k1 as BIGINT)" \
        http://host:port/api/test/bigint/_stream_load

注意

如果原始值是浮点值（例如 12.0），它将被转换为 NULL。 如果您想强制将此类型转换为 BIGINT，请参见以下示例

    curl --location-trusted -u <username>:<password> -T ~/user_data/bigint \
        -H "columns: tmp_k1, k1=cast(cast(tmp_k1 as DOUBLE) as BIGINT)" \
        http://host:port/api/test/bigint/_stream_load

    MySQL > select cast(cast ("11.2" as double) as bigint);
    +----------------------------------------+
    | CAST(CAST('11.2' AS DOUBLE) AS BIGINT) |
    +----------------------------------------+
    |                                     11 |
    +----------------------------------------+