CAST
CAST
Description
CAST 函数用于 SQL 查询中的数据类型转换。 它通常用于将一种数据类型转换为另一种数据类型，例如将字符串转换为整数、将整数转换为字符串等。
Syntax
CAST (src_type as dst_type)
将 src_type 转成指定的 dst_type 类型
Example
- 转常量，或表中某列
mysql> select cast('1234' as int);
+---------------------+
| cast('1234' as INT) |
+---------------------+
| 1234 |
+---------------------+
- 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 。Doris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)
对于DECIMALV3类型，CAST 会进行四舍五入：
mysql> select cast (1.115 as DECIMALV3(16, 2));
+---------------------------------+
| cast(1.115 as DECIMALV3(16, 2)) |
+---------------------------------+
| 1.12 |
+---------------------------------+
Keywords
CAST
