diff --git a/docs/reference/sql/data-types.md b/docs/reference/sql/data-types.md index 55e0066ed..7f1d6800f 100644 --- a/docs/reference/sql/data-types.md +++ b/docs/reference/sql/data-types.md @@ -31,6 +31,12 @@ The maximum capacities of `String` and `Binary` are determined by their encoding | `Float32` | 32-bit IEEE754 floating point values | 4 Bytes | | `Float64` | Double precision IEEE 754 floating point values | 8 Bytes | +:::tip NOTE +The descriptions here refer to **GreptimeDB native type information**, which are measured in **bits**. +However, when using **SQL**, follow the conventions of **PostgreSQL** and **MySQL**, where types like `INT2`, `INT4`, `INT8`, `FLOAT4` and `FLOAT8` are defined in **bytes**. +For example, in an SQL statement, `INT8` actually corresponds to **BigInt** (8 bytes, 64 bits). +::: + ## Decimal Type 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. @@ -303,24 +309,38 @@ INSERT INTO bools(b) VALUES (TRUE), (FALSE); For users migrating from MySQL or PostgreSQL to GreptimeDB, GreptimeDB supports the following alias types. -| Data Type | Alias Types | -| ---------------------- | --------------------------------------------------------------- | -| `String` | `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` | -| `Binary` | `Varbinary` | -| `Int8` | `TinyInt` | -| `Int16` | `SmallInt` | -| `Int32` | `Int` | -| `Int64` | `BigInt` | -| `UInt8` | `UnsignedTinyInt` | -| `UInt16` | `UnsignedSmallInt` | -| `UInt32` | `UnsignedInt` | -| `UInt64` | `UnsignedBigInt` | -| `Float32` | `Float` | -| `Float64` | `Double` | -| `TimestampSecond` | `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` | -| `TimestampMillisecond` | `Timestamp`, `Timestamp_ms`, `Timestamp(3)` | -| `TimestampMicroSecond` | `Timestamp_us`, `Timestamp(6)` | -| `TimestampNanosecond` | `Timestamp_ns`, `Timestamp(9)` | + +| SQL Datatype Alias | Native Datatype | +| --------------------------------------------------------------- | ---------------------- | +| `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` | `String` | +| `Varbinary` | `Binary` | +| `TinyInt` | `Int8` | +| `SmallInt`, `Int2` | `Int16` | +| `Int`, `Int4` | `Int32` | +| `BigInt`, `Int8` | `Int64` | +| `UnsignedTinyInt` | `UInt8` | +| `UnsignedSmallInt` | `UInt16` | +| `UnsignedInt` | `UInt32` | +| `UnsignedBigInt` | `UInt64` | +| `Float`, `Float4` | `Float32` | +| `Double`, `Float8` | `Float64` | +| `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` | `TimestampSecond` | +| `Timestamp`, `Timestamp_ms`, `Timestamp(3)` | `TimestampMillisecond` | +| `Timestamp_us`, `Timestamp(6)` | `TimestampMicroSecond` | +| `Timestamp_ns`, `Timestamp(9)` | `TimestampNanosecond` | + +:::warning Note +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. + +Specifically: +- `Int2` = 2 bytes = `SmallInt` (16-bit) +- `Int4` = 4 bytes = `Int` (32-bit) +- `Int8` = 8 bytes = `BigInt` (64-bit) +- `Float4` = 4 bytes = `Float` (32-bit) +- `Float8` = 8 bytes = `Double` (64-bit) + +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). +::: You can use these alias types when creating tables. For example, use `Varchar` instead of `String`, `Double` instead of `Float64`, and `Timestamp(0)` instead of `TimestampSecond`. diff --git a/i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/data-types.md b/i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/data-types.md index c53606921..223e1d1b8 100644 --- a/i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/data-types.md +++ b/i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/data-types.md @@ -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 | `Float32` | 32 位 IEEE 754 浮点数 | 4 字节 | | `Float64` | 双精度 IEEE 754 浮点数 | 8 字节 | +:::tip 注意 +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。 +例如，在 SQL 语句中，`INT8` 实际上对应 `BigInt`（8 个字节，64 位）。 +::: + ## Decimal 类型 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。 @@ -303,24 +308,37 @@ INSERT INTO bools(b) VALUES (TRUE), (FALSE); 对于从 MySQL 或 PostgreSQL 迁移到 GreptimeDB 的用户，GreptimeDB 支持以下类型别名。 -| 数据类型 | 别名 | -| ---------------------- | --------------------------------------------------------------- | -| `String` | `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` | -| `Binary` | `Varbinary` | -| `Int8` | `TinyInt` | -| `Int16` | `SmallInt` | -| `Int32` | `Int` | -| `Int64` | `BigInt` | -| `UInt8` | `UnsignedTinyInt` | -| `UInt16` | `UnsignedSmallInt` | -| `UInt32` | `UnsignedInt` | -| `UInt64` | `UnsignedBigInt` | -| `Float32` | `Float` | -| `Float64` | `Double` | -| `TimestampSecond` | `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` | -| `TimestampMillisecond` | `Timestamp`, `Timestamp_ms` , `Timestamp(3)` | -| `TimestampMicroSecond` | `Timestamp_us`, `Timestamp(6)` | -| `TimestampNanosecond` | `Timestamp_ns`, `Timestamp(9)` | +| SQL 类型别名 | Native 数据类型 | +| --------------------------------------------------------------- | ---------------------- | +| `Text`, `TinyText`, `MediumText`, `LongText`, `Varchar`, `Char` | `String` | +| `Varbinary` | `Binary` | +| `TinyInt` | `Int8` | +| `SmallInt`, `Int2` | `Int16` | +| `Int`, `Int4` | `Int32` | +| `BigInt`, `Int8` | `Int64` | +| `UnsignedTinyInt` | `UInt8` | +| `UnsignedSmallInt` | `UInt16` | +| `UnsignedInt` | `UInt32` | +| `UnsignedBigInt` | `UInt64` | +| `Float`, `Float4` | `Float32` | +| `Double`, `Float8` | `Float64` | +| `Timestamp_s`, `Timestamp_sec`, `Timestamp(0)` | `TimestampSecond` | +| `Timestamp`, `Timestamp_ms`, `Timestamp(3)` | `TimestampMillisecond` | +| `Timestamp_us`, `Timestamp(6)` | `TimestampMicroSecond` | +| `Timestamp_ns`, `Timestamp(9)` | `TimestampNanosecond` | + +:::warning 注意 +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）。 + +具体来说： +- `Int2` = 2 字节 = `SmallInt`（16 位） +- `Int4` = 4 字节 = `Int`（32 位） +- `Int8` = 8 字节 = `BigInt`（64 位） +- `Float4` = 4 字节 = `Float`（32 位） +- `Float8` = 8 字节 = `Double`（64 位） + +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）。 +::: 在创建表时也可以使用这些别名类型。 例如，使用 `Varchar` 代替 `String`，使用 `Double` 代替 `Float64`，使用 `Timestamp(0)` 代替 `TimestampSecond`。