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docs: update numeric type aliases aligned with PostgreSQL and MySQL (#2231)
Signed-off-by: Dennis Zhuang <[email protected]> Co-authored-by: copilot-swe-agent[bot] <[email protected]> Co-authored-by: killme2008 <[email protected]> Co-authored-by: Dennis Zhuang <[email protected]>
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‎docs/reference/sql/data-types.md‎

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@@ -31,6 +31,12 @@ The maximum capacities of `String` and `Binary` are determined by their encoding
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| `Float32` | 32-bit IEEE754 floating point values | 4 Bytes |
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| `Float64` | Double precision IEEE 754 floating point values | 8 Bytes |
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:::tip NOTE
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The descriptions here refer to **GreptimeDB native type information**, which are measured in **bits**.
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However, when using **SQL**, follow the conventions of **PostgreSQL** and **MySQL**, where types like `INT2`, `INT4`, `INT8`, `FLOAT4` and `FLOAT8` are defined in **bytes**.
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For example, in an SQL statement, `INT8` actually corresponds to **BigInt** (8 bytes, 64 bits).
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:::
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## Decimal Type
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GreptimeDB supports the `decimal` type, a fixed-point type represented as `decimal(precision, scale)`, where `precision` is the total number of digits, and `scale` is the number of digits in the fractional part. For example, `123.45` has a precision of 5 and a scale of 2.
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For users migrating from MySQL or PostgreSQL to GreptimeDB, GreptimeDB supports the following alias types.
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| Data Type | Alias Types |
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| ---------------------- | --------------------------------------------------------------- |
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| `String` | `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` |
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| `Binary` | `Varbinary` |
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| `Int8` | `TinyInt` |
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| `Int16` | `SmallInt` |
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| `Int32` | `Int` |
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| `Int64` | `BigInt` |
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| `UInt8` | `UnsignedTinyInt` |
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| `UInt16` | `UnsignedSmallInt` |
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| `UInt32` | `UnsignedInt` |
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| `UInt64` | `UnsignedBigInt` |
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| `Float32` | `Float` |
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| `Float64` | `Double` |
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| `TimestampSecond` | `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` |
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| `TimestampMillisecond` | `Timestamp`, `Timestamp_ms`, `Timestamp(3)` |
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| `TimestampMicroSecond` | `Timestamp_us`, `Timestamp(6)` |
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| `TimestampNanosecond` | `Timestamp_ns`, `Timestamp(9)` |
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| SQL Datatype Alias | Native Datatype |
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| --------------------------------------------------------------- | ---------------------- |
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| `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` | `String` |
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| `Varbinary` | `Binary` |
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| `TinyInt` | `Int8` |
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| `SmallInt`, `Int2` | `Int16` |
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| `Int`, `Int4` | `Int32` |
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| `BigInt`, `Int8` | `Int64` |
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| `UnsignedTinyInt` | `UInt8` |
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| `UnsignedSmallInt` | `UInt16` |
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| `UnsignedInt` | `UInt32` |
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| `UnsignedBigInt` | `UInt64` |
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| `Float`, `Float4` | `Float32` |
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| `Double`, `Float8` | `Float64` |
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| `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` | `TimestampSecond` |
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| `Timestamp`, `Timestamp_ms`, `Timestamp(3)` | `TimestampMillisecond` |
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| `Timestamp_us`, `Timestamp(6)` | `TimestampMicroSecond` |
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| `Timestamp_ns`, `Timestamp(9)` | `TimestampNanosecond` |
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:::warning Note
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The type aliases `Int2`, `Int4`, `Int8`, `Float4`, and `Float8` follow the PostgreSQL and MySQL convention where these identifiers refer to the number of **bytes** (not bits) in the type.
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Specifically:
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- `Int2` = 2 bytes = `SmallInt` (16-bit)
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- `Int4` = 4 bytes = `Int` (32-bit)
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- `Int8` = 8 bytes = `BigInt` (64-bit)
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- `Float4` = 4 bytes = `Float` (32-bit)
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- `Float8` = 8 bytes = `Double` (64-bit)
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Note: GreptimeDB's native type names (like `UInt8`, `Int32`, `Int64`) refer to the number of **bits**, while the SQL aliases `Int2`, `Int4`, and `Int8` refer to the number of **bytes** following PostgreSQL/MySQL conventions. For example, the native type `Int8` is an 8-**bit** integer (`TinyInt`, 1 byte), while the SQL alias `INT8` maps to an 8-**byte** integer (`BigInt`, 64-bit).
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:::
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You can use these alias types when creating tables.
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For example, use `Varchar` instead of `String`, `Double` instead of `Float64`, and `Timestamp(0)` instead of `TimestampSecond`.

‎i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/data-types.md‎

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@@ -31,6 +31,11 @@ SQL 数据类型定义了列可以存储的数据类型。当您运行 `DESC TAB
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| `Float32` | 32 位 IEEE 754 浮点数 | 4 字节 |
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| `Float64` | 双精度 IEEE 754 浮点数 | 8 字节 |
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:::tip 注意
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这里的描述指的是 GreptimeDB 原生类型信息，这些类型都是以 位（bits） 为单位的。但是，在使用 SQL 时，请遵循 PostgreSQL 和 MySQL 的惯例，其中 `INT2`、`INT4`、`INT8`、`FLOAT4` 和 `FLOAT8` 等类型都是以 字节（bytes） 为单位定义的。
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例如，在 SQL 语句中，`INT8` 实际上对应 `BigInt`（8 个字节，64 位）。
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:::
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## Decimal 类型
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GreptimeDB 支持 `decimal` 类型，这是一种定点类型，表示为 `decimal(precision, scale)`，其中 `precision` 是总位数，`scale` 是小数部分的位数。例如，`123.45` 的总位数为 5，小数位数为 2。
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对于从 MySQL 或 PostgreSQL 迁移到 GreptimeDB 的用户，GreptimeDB 支持以下类型别名。
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| 数据类型 | 别名 |
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| ---------------------- | --------------------------------------------------------------- |
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| `String` | `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` |
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| `Binary` | `Varbinary` |
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| `Int8` | `TinyInt` |
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| `Int16` | `SmallInt` |
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| `Int32` | `Int` |
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| `Int64` | `BigInt` |
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| `UInt8` | `UnsignedTinyInt` |
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| `UInt16` | `UnsignedSmallInt` |
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| `UInt32` | `UnsignedInt` |
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| `UInt64` | `UnsignedBigInt` |
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| `Float32` | `Float` |
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| `Float64` | `Double` |
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| `TimestampSecond` | `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` |
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| `TimestampMillisecond` | `Timestamp`, `Timestamp_ms` , `Timestamp(3)` |
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| `TimestampMicroSecond` | `Timestamp_us`, `Timestamp(6)` |
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| `TimestampNanosecond` | `Timestamp_ns`, `Timestamp(9)` |
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| SQL 类型别名 | Native 数据类型 |
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| --------------------------------------------------------------- | ---------------------- |
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| `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` | `String` |
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| `Varbinary` | `Binary` |
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| `TinyInt` | `Int8` |
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| `SmallInt`, `Int2` | `Int16` |
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| `Int`, `Int4` | `Int32` |
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| `BigInt`, `Int8` | `Int64` |
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| `UnsignedTinyInt` | `UInt8` |
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| `UnsignedSmallInt` | `UInt16` |
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| `UnsignedInt` | `UInt32` |
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| `UnsignedBigInt` | `UInt64` |
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| `Float`, `Float4` | `Float32` |
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| `Double`, `Float8` | `Float64` |
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| `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` | `TimestampSecond` |
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| `Timestamp`, `Timestamp_ms`, `Timestamp(3)` | `TimestampMillisecond` |
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| `Timestamp_us`, `Timestamp(6)` | `TimestampMicroSecond` |
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| `Timestamp_ns`, `Timestamp(9)` | `TimestampNanosecond` |
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:::warning 注意
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类型别名 `Int2`、`Int4`、`Int8`、`Float4` 和 `Float8` 遵循 PostgreSQL 和 MySQL 的约定，这些标识符表示类型中的**字节**数（而非位数）。
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具体来说：
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- `Int2` = 2 字节 = `SmallInt`（16 位）
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- `Int4` = 4 字节 = `Int`（32 位）
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- `Int8` = 8 字节 = `BigInt`（64 位）
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- `Float4` = 4 字节 = `Float`（32 位）
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- `Float8` = 8 字节 = `Double`（64 位）
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注意：GreptimeDB 的原生类型名称（如 `UInt8`、`Int32`、`Int64`）表示**位**数，而 SQL 类型别名 `Int2`、`Int4` 和 `Int8` 遵循 PostgreSQL/MySQL 约定表示**字节**数。例如，原生类型 `Int8` 是 8 **位**整数（`TinyInt`, 1 字节），而 SQL 别名 `INT8` 映射到 8 **字节**整数（`BigInt`，64 位）。
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在创建表时也可以使用这些别名类型。
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例如，使用 `Varchar` 代替 `String`，使用 `Double` 代替 `Float64`，使用 `Timestamp(0)` 代替 `TimestampSecond`。

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