Function registerDataTypeArray

src/DataTypes/DataTypeArray.cpp:118–232

void registerDataTypeArray(DataTypeFactory & factory)
{
    factory.registerDataType("Array", create, DataTypeFactory::Case::Sensitive, Documentation{
            .description = R"DOCS_MD(
An array of `T`-type items, with the starting array index as 1. `T` can be any data type, including an array.

## Creating an Array {#creating-an-array}

You can use a function to create an array:

```sql
array(T)
```

You can also use `[]`.

```sql
[]
```

Example of creating an array:

```sql
SELECT array(1, 2) AS x, toTypeName(x)
```

```text
┌─x─────┬─toTypeName(array(1, 2))─┐
│ [1,2] │ Array(UInt8)            │
└───────┴─────────────────────────┘
```

```sql
SELECT [1, 2] AS x, toTypeName(x)
```

```text
┌─x─────┬─toTypeName([1, 2])─┐
│ [1,2] │ Array(UInt8)       │
└───────┴────────────────────┘
```

## Working with Data Types {#working-with-data-types}

When creating an array on the fly, ClickHouse automatically defines the argument type as the narrowest data type that can store all the listed arguments. If there are any [Nullable](/sql-reference/data-types/nullable) or literal [NULL](/operations/settings/formats#input_format_null_as_default) values, the type of an array element also becomes [Nullable](../../sql-reference/data-types/nullable.md).

If ClickHouse couldn't determine the data type, it generates an exception. For instance, this happens when trying to create an array with strings and numbers simultaneously (`SELECT array(1, 'a')`).

Examples of automatic data type detection:

```sql
SELECT array(1, 2, NULL) AS x, toTypeName(x)
```

```text
┌─x──────────┬─toTypeName(array(1, 2, NULL))─┐
│ [1,2,NULL] │ Array(Nullable(UInt8))        │
└────────────┴───────────────────────────────┘