Single Select [select]

The “Single select [select]” attribute creates a 1:n relation to another table — either a MetaModels table or any Contao table (e.g. tl_member, tl_page). The ID of the selected record is stored in the database. Typical use cases:

• Assigning a product to a category

• Linking an article with an author

• Selecting a Contao page as the target page

The selection in the backend can be displayed as a dropdown, radio button list, or tree picker.

Note

For relations between two multilingual MetaModels, the monolingual variant “Single select” should be used — MetaModels automatically recognizes the language and switches accordingly.

See also

For special cases with their own language column in the referenced table, Translated Single Select [select] is available.

Installation

The attribute is installed via the Contao Manager or Composer:

composer require metamodels/attribute_select

Settings when Creating the Attribute

In addition to the general attribute settings (name, column name, description, override variants), the attribute offers the following specific options:

Option	Description
Source table	The table from which the selection values are obtained. MetaModels tables as well as all Contao database tables are available.
Value column	The column of the source table whose content is displayed as the label in the selection list.
ID column	The column that serves as the unique identifier (stored value). Default: id.
Alias column	The column used as a readable identifier in filter widgets. If unsure, select the same column as the ID column.
Selection sorting	Column by which the selection list is sorted.
Sort direction	Ascending (A → Z) or descending (Z → A).
SQL (WHERE condition)	Optional SQL WHERE condition to restrict the selection list. The alias sourceTable represents the source table (e.g. sourceTable.published = '1'). The condition does not filter when the widget type “Popup picker” is selected.
Filter	Selection of a MetaModels filter set for dynamic restriction of options.
Filter parameters	Default values for the parameters of the selected filter set.

Settings in Render Settings

The single select attribute has no specific render settings. In the attribute list of a render setting, the usual options are available:

Option	Description
Template	Selection of a custom template for the output of the linked value.
CSS class	Optional CSS class added to the output element.

Settings in the Input Form

When the attribute is added to an input form, the following options are available:

Display

Option	Description
Backend class	CSS classes for the display of the field in the backend form.
Template for backend	Selection of a custom widget template for the backend form.
Template for frontend	Selection of a custom widget template for frontend editing (only available if the “Frontend Editing” extension is installed).
Display type	Display type of the selection: Select menu — Classic dropdown menu Radio button list — All options as radio buttons Popup picker — Selection via a tree picker (for hierarchical source tables such as tl_page or tl_files)
Lowest level (tree)	For tree picker: records below this level are not selectable (0 = no restriction).
Highest level (tree)	For tree picker: records above this level are not selectable (0 = no restriction).

Functions

Option	Description
Required field	Makes the field a required field.
Show empty option	Displays an empty selection option so that no pre-selection is made.

Overview (backend filter and search)

Option	Description
Filterable	The attribute is available in the backend as a filter criterion.
Searchable	The attribute is available in the backend as a search field.

Filter Rules

The single select attribute can be used with the following filter rules:

Filter rule	Note
Single select	Filters by a selected value from the source table; e.g. all products of a specific category.
Filter on attribute of model with a relation	Filters MetaModel items based on an attribute value of the linked MetaModel; e.g. all products whose category has a specific characteristic.

Special Functions

Database storage

The ID of the selected record is stored as int(11) NULL in the MetaModel table.

Source table types

The following can be selected as the source table:

• MetaModels tables — with full access to all attributes

• Non-translated Contao tables — any table from the Contao database

• SQL tables — direct table selection via SQL alias

SQL WHERE condition

In the WHERE condition, the alias sourceTable represents the source table. Example for filtering on published entries:

sourceTable.published = '1'