Function registerDataTypeEnum

src/DataTypes/DataTypeEnum.cpp:459–650

}

void registerDataTypeEnum(DataTypeFactory & factory)
{
    factory.registerDataType("Enum8", [](const ASTPtr & arguments)
    {
        return createExact<DataTypeEnum8>(arguments, false);
    }, DataTypeFactory::Case::Sensitive,
        Documentation{
            .description = R"DOCS_MD(
An enumeration type that stores values as 8-bit signed integers (`Int8`), allowing up to 256 named values in the range `[-128, 127]`. Each `'string' = integer` pair maps a human-readable name to its stored numeric value. Use it instead of `Enum16` when the set of values is small to save space.
)DOCS_MD",
            .syntax = "Enum8('name1' = num1, 'name2' = num2, ...)",
            .related = {"Enum"},
        });
    factory.registerDataType("Enum16", [](const ASTPtr & arguments)
    {
        return createExact<DataTypeEnum16>(arguments, false);
    }, DataTypeFactory::Case::Sensitive,
        Documentation{
            .description = R"DOCS_MD(
An enumeration type that stores values as 16-bit signed integers (`Int16`), allowing up to 65536 named values in the range `[-32768, 32767]`. Each `'string' = integer` pair maps a human-readable name to its stored numeric value. Use it when the set of named values is too large to fit in `Enum8`.
)DOCS_MD",
            .syntax = "Enum16('name1' = num1, 'name2' = num2, ...)",
            .related = {"Enum"},
        });
    factory.registerDataType("Enum", [](const ASTPtr & arguments)
    {
        return create(arguments, false);
    }, DataTypeFactory::Case::Sensitive,
        Documentation{
            .description = R"DOCS_MD(
Enumerated type consisting of named values.

Named values can be declared as `'string' = integer` pairs or `'string'` names . ClickHouse stores only numbers, but supports operations with the values through their names.

ClickHouse supports:

- 8-bit `Enum`. It can contain up to 256 values enumerated in the `[-128, 127]` range.
- 16-bit `Enum`. It can contain up to 65536 values enumerated in the `[-32768, 32767]` range.

ClickHouse automatically chooses the type of `Enum` when data is inserted. You can also use `Enum8` or `Enum16` types to be sure in the size of storage.

## Usage Examples {#usage-examples}

Here we create a table with an `Enum8('hello' = 1, 'world' = 2)` type column:

```sql
CREATE TABLE t_enum
(
    x Enum('hello' = 1, 'world' = 2)
)
ENGINE = TinyLog
```

Similarly, you could omit numbers. ClickHouse will assign consecutive numbers automatically. Numbers are assigned starting from 1 by default.

```sql
CREATE TABLE t_enum
(