SQL Field Guide
The SQL form field provides a drop down list of entries obtained by running a query on the Joomla database.
Field Settings
Select: It is the SELECT clause of the SQL statement. This is required. Enter the comma separated names of the columns to select. For example: id,title
From: It is the FROM clause of the SQL statement. This is required. This is the name of the database table. You need to add prefix #__ (hash symbol with two underscores) before the table name. For example, "#__content".
Where: It is the WHERE clause of the SQL statement. You can add conditions to filter the records.
Group By: It is the GROUP BY clause of the SQL statement.
Order By: It is the ORDER BY clause of the SQL statement. For example, to order the records in ascending order by title, enter "title ASC".
Key Field: It is the name of the column that will contain values for the parameter. This is saved in the database. For example, id.
Value Field: It is the name of the column that will contain values to be shown to the user in the drop-down list. For example, title.
Header: It will add an entry, with an empty value, at the top of the list of drop down options. Use this setting to add a "- Select something -" entry to the list.
Multiple: Whether multiple values can be selected from the dropdown list.
Form Layout: Choose the layout that will be used to render the field.