cast.md

CAST

功能

将 input 转成指定的(type)的值, 如 cast (input as BIGINT) 将当前列 input 转换为 BIGINT 类型的值

语法

cast(input as type)

参数说明

input: 待转类型的参数

type: 目标类型

返回值说明

返回值的数据类型为 type(目标类型)

示例

1. 转常量，或表中某列

   MySQL > select cast (1 as BIGINT);
   +-------------------+
   | CAST(1 AS BIGINT) |
   +-------------------+
   |                 1 |
   +-------------------+
   

2. 转导入的原始数据

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

   注：在导入中, 由于原始类型均为 String, 将值为浮点的原始数据做 cast 的时候数据会被转换成 NULL , 比如 12.0 StarRocks 目前不会对原始数据做截断

   如果想强制将这种类型的原始数据 cast to int 的话, 请看下面写法:

   curl --location-trusted -u root: -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 |
   +----------------------------------------+
   1 row in set (0.00 sec)