J3.x:Adding custom fields/Sql Field
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Provides a drop down list of entries obtained by running a query on the Joomlaǃ Database. The first results column returned by the query provides the values for the drop down box.
Special options within this field are:
Allow multiple values to be selected - if activated.
The SQL query which will provide the data for the dropdown list. The query must return two columns; one called 'value' which will hold the values of the list items; the other called 'text' containing the text in the drop-down list.
Creating the field
Let's say you create a field with the options shown in the next figure.
Using the field in the backend
In the backend while creating an article or a contact you see the field like in the following imageː
Using the field in the frontend
In the frontend, you can see the field as you see in the following image. The option Automatic display is responsible for the position of the field and your template is responsible for the design of the field.
Fields are only displayed in the frontend if you have filled them with data in the article. If it is not a required field, can you forget it?