Type.TableSchema

Type

Returns a table describing the columns of a table type, including column names, positions, type names, and kinds.

Syntax

Type.TableSchema(type as type) as table

Parameters

Name	Type	Required	Description
`type`	`type`	Yes	A table type whose schema is described.

Return Value

table — A table with columns Name, Position, TypeName, and Kind describing each column of the table type.

Remarks

Type.TableSchema returns a table that describes the columns declared in a table type. The result has four columns:

- Name — the column name as text - Position — the zero-based column index (0 for the first column) - TypeName — the column's type as a text string (e.g., "number", "text", "nullable number") - Kind — the kind of the type as text (e.g., "Primitive" for type number, "Nullable" for type nullable number)

This function operates on a table type value — not the table itself. Pass Value.Type(table) to obtain the table's type before calling Type.TableSchema.

Type.TableSchema provides a human-readable, table-formatted alternative to Type.TableColumn for inspecting schemas. Common uses include:

- Programmatic schema inspection: determining column count, order, names, and types in one call - Documentation generation: producing a schema summary that can be returned or logged - Generic validation: filtering for columns of a specific kind or type name before applying transforms

For structured programmatic access to individual column types, prefer Type.TableColumn. For key information, use Type.TableKeys.

Examples

Example 1: Get the full schema of a typed table

let
    T = #table(
        type table [OrderID = number, Product = text, UnitPrice = nullable number],
        {{1, "Widget A", 25.0}}
    ),
    Schema = Type.TableSchema(Value.Type(T))
in
    Schema

Applied Steps

The final output — the schema table showing all three columns with their positions, type names, and kinds.

	Name	Position	TypeName	Kind
1	OrderID	0	number	Primitive
2	Product	1	text	Primitive
3	UnitPrice	2	nullable number	Nullable

Example 2: Count columns declared in the Sales table type

Table.RowCount(Type.TableSchema(Value.Type(Sales)))

Result

	Result
1	8

Example 3: Find all nullable columns in a table type

let
    T = #table(
        type table [OrderID = number, Product = text, Notes = nullable text],
        {{1, "Widget A", null}}
    ),
    Schema = Type.TableSchema(Value.Type(T)),
    NullableCols = Table.SelectRows(Schema, each [Kind] = "Nullable")
in
    NullableCols[Name]