Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/data-types/table-type/
Documentation version: v5.3.2

# Table types

A table type describes tabular data composed of named fields and rows. Each field has a value type. For example, `TABLE {id INT64, name STRING}` describes a table with an `id` field of type `INT64` and a `name` field of type `STRING`.

Table types cannot be used as node or edge property types.

## View a table type

Use the `typeof()` function to view the type of a table variable:

````
'''
TABLE t TYPED TABLE {id INT64, name STRING} =
    {id: 10001, name: 'Alice'},
    {id: 10002, name: 'Bob'}
RETURN typeof(t) AS t_type
'''

````

Return:

````
+-------------------------------+
| t_type                        |
+-------------------------------+
| TABLE {id INT64, name STRING} |
+-------------------------------+

````

The returned type contains the name and value type of each field.

## Table types and table variables

A table type describes the structure of tabular data, whereas a table variable stores or refers to the data:

````
TABLE t TYPED TABLE {id INT64, name STRING}

````

In this declaration:

- `t` is the table variable.
- `TABLE {id INT64, name STRING}` is its table type.
- The first `TABLE` keyword introduces the table variable declaration.

For the complete declaration syntax, see [Table variables](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/variable-definition/table-variable/).

## Use a table type as a procedure parameter

A user-defined procedure (UDP) can accept a table through a parameter declared with `TABLE`:

````
parameter_name TABLE

````

In this syntax, `TABLE` accepts a table variable passed by the caller. For more information, see [CREATE PROCEDURE](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/procedures/create/#parameter_type).

## Usage

Table types are mainly used for:

- Table variables that store intermediate data or results.
- UDP parameters that receive tables.
- Data exchanged through `IMPORT` and `EXPORT`.

## Table variables in NebulaGraph Database Developer Edition

In NebulaGraph Database Developer Edition, the field names and types of a table variable can also be inferred from an initializer or query result. Local table variables can be iterated with `FOR`.

## Limitations

- Table types cannot be used as node or edge property types.
- The values written to a table must be compatible with its field types.

## See also

- [Table variables](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/variable-definition/table-variable/)
- [typeof()](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/functions/system/#typeof)
- [IMPORT](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/in-out/import/)
- [EXPORT](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/in-out/export/)