Type.TableSchema

Type.TableSchema is a Power Query M function that returns a table describing the columns of a given table type. The function returns a table with information about the columns in the input table type, as described in the Table.Schema documentation.

Compatible with: Power BI Service Power BI Desktop Excel Microsoft 365

Syntax

Type.TableSchema( tableType as type ) as table

Column Name	Description
Name	The column name.
Position	The 0-based position of the column in table.
TypeName	The name of the type of the column.
Kind	The kind of the type of the column.
IsNullable	Whether the column can contain null values.
NumericPrecisionBase	The numeric base (for example, base-2 or base-10) of the NumericPrecision and NumericScale fields.
NumericPrecision	The precision of a numeric column in the base specified by NumericPrecisionBase. This is the maximum number of digits that can be represented by a value of this type (including fractional digits).
NumericScale	The scale of a numeric column in the base specified by NumericPrecisionBase. This is the number of digits in the fractional part of a value of this type. A value of 0 indicates a fixed scale with no fractional digits. A value of null indicates the scale is not known (either because it is floating or not defined).
DateTimePrecision	The maximum number of fractional digits supported in the seconds portion of a date or time value.
MaxLength	The maximum number of characters permitted in a text column, or the maximum number of bytes permitted in a binary column.
IsVariableLength	Indicates whether this column can vary in length (up to MaxLength) or if it is of fixed size.
NativeTypeName	The name of the type of the column in the native type system of the source (for example, nvarchar for SQL Server).
NativeDefaultExpression	The default expression for a value of this column in the native expression language of the source (for example, 42 or newid() for SQL Server).
NativeExpression
Description	The description of the column.
IsWritable
FieldCaption

Description

The Type.TableSchema function returns a table describing the columns of the input tableType. It returns similar columns as the Table.Schema function. The operation returns the following fields:

Examples

Suppose you have a table in a step called source. To describe the columns within that table you can make use of the Type.TableSchema function.

You would first need to retrieve what type the table has. With a table called ‘Source’ you can do that by using the Value.Type function:

Value.Type( Source )

You can then pass this abstract table type to the Type.TableSchema function.

Type.TableSchema( Value.Type( Source ) )

This returns a table with 17 columns, describing the contents of your table.

Related functions

Other functions related to Type.TableSchema are:

• Type.TableColumn
• Type.TableRow

Contribute » | Contributors: Rick de Groot
Microsoft documentation: https://learn.microsoft.com/en-us/powerquery-m/type-tableschema