Use brackets if your column name does not conform to these rules
The exception of these rules is when a column name is enclosed in brackets (for example, «Products.[Product Category]» . To include spaces or unicode characters in the data source column name, use this format:«DataSource.[Column Name]»
For example: «Employees.[Street Address]» . The [Column Name] format allows you to match any SQL column name exactly. Legal characters within the brackets include every character except parentheses () or brackets [].
When creating these fields with WordApplication or editing the field codes manually, the merge field name must be enclosed in quotes. For example, it should be { MERGEFIELD "[data source].[column name]" }. Any modifiers must also go in the quotes, but the formatting options must go after the quotes.