数据类型
- 整数类型的 Unsigned 版本
- Variable-sized 类型的限制
  - 为 timestamp 列选择数据类型

数据类型

GreptimeDB 支持下列数据类型：

Type name	Description	Synonyms	Size
`tinyint`	8-bit signed small integers between -128~127		1 Byte
`smallint`	16-bit signed big integers between -32768~32767		2 Bytes
`int`	32-bit signed integers between -2147483648~2147483647	`integer`	4 Bytes
`bigint`	64-bit signed big integers between -9223372036854775808~9223372036854775807		8 Bytes
`varchar`	UTF-8 encoded strings	`text` /`string` / `char`	The length of the strings
`float`	32-bit IEEE754 floating point values		4 Bytes
`double`	Double precision IEEE 754 floating point values		8 Bytes
`boolean`	Boolean values		1 Byte
`varbinary`	Variable length binary values		The length of the data + 2 bytes
`date`	32-bit date values		4 Bytes
`datetime`	64-bit datetime values		8 Bytes
`timestamp[(0/3/6/9)]`	64-bit timestamp values with optional precision. For example, `timestamp(0)` represents timestamp type with seconds precision, `timestamp(3)` represents milliseconds precision, `timestamp(6)` for microseonds and `timestamp(9)` for nanoseconds. If no precision is given, the timestamp is in milliseconds precision by default.		8 Bytes

整数类型的 Unsigned 版本

int / tinyint / smallint / bigint 有 unsigned 版本，相应的值范围如下：

int unsigned: 0~4294967295
tinyint unsigned: 0~255
smallint unsigned: 0~65535
bigint unsigned: 0~18446744073709551615

Variable-sized 类型的限制

variable-sized 类型的最大容量, 例如 string 和 varbinary，取决于它们的编码和存储引擎处理它们的方式。

例如，string 值被编码为 UTF-8。如果所有字符都是 3 字节长度，则该字段可以存储 715827882 个字符。对于 varbinary 类型，最多可以存储 2147483647 字节。

为 timestamp 列选择数据类型

GreptimeDB 允许用户为时间戳索引列设置为 bigint 或 timestamp 类型。 bigint 和 timestamp 都被解释为毫秒精度的时间戳。

sql

# using TIMESTAMP as timestamp column data type
CREATE TABLE monitor (
    host STRING,
    ts TIMESTAMP, 
    cpu DOUBLE DEFAULT 0,
    memory DOUBLE,
    TIME INDEX (ts),
    PRIMARY KEY(host)) ENGINE=mito WITH(regions=1);
# using BIGINT as timestamp column data type is also allowed
CREATE TABLE monitor (
    host STRING,
    ts BIGINT, 
    cpu DOUBLE DEFAULT 0,
    memory DOUBLE,
    TIME INDEX (ts),
    PRIMARY KEY(host)) ENGINE=mito WITH(regions=1);