Function registerDataTypeTuple

src/DataTypes/DataTypeTuple.cpp:497–712

void registerDataTypeTuple(DataTypeFactory & factory)
{
    factory.registerDataType("Tuple", create, DataTypeFactory::Case::Sensitive, Documentation{
            .description = R"DOCS_MD(
A tuple of elements, each having an individual [type](/sql-reference/data-types). Tuple must contain at least one element.

Tuples are used for temporary column grouping. Columns can be grouped when an IN expression is used in a query, and for specifying certain formal parameters of lambda functions. For more information, see the sections [IN operators](../../sql-reference/operators/in.md) and [Higher order functions](/sql-reference/functions/overview#higher-order-functions).

Tuples can be the result of a query. In this case, for text formats other than JSON, values are comma-separated in `()`. In JSON formats, tuples are output as arrays (in `[]`).

## Creating Tuples {#creating-tuples}

You can use a function to create a tuple:

```sql
tuple(T1, T2, ...)
```

Example of creating a tuple:

```sql
SELECT tuple(1, 'a') AS x, toTypeName(x)
```

```text
┌─x───────┬─toTypeName(tuple(1, 'a'))─┐
│ (1,'a') │ Tuple(UInt8, String)      │
└─────────┴───────────────────────────┘
```

A Tuple can contain a single element

Example:

```sql
SELECT tuple('a') AS x;
```

```text
┌─x─────┐
│ ('a') │
└───────┘
```

Syntax `(tuple_element1, tuple_element2)` may be used to create a tuple of several elements without calling the `tuple()` function.

Example:

```sql
SELECT (1, 'a') AS x, (today(), rand(), 'someString') AS y, ('a') AS not_a_tuple;
```

```text
┌─x───────┬─y──────────────────────────────────────┬─not_a_tuple─┐
│ (1,'a') │ ('2022-09-21',2006973416,'someString') │ a           │
└─────────┴────────────────────────────────────────┴─────────────┘
```