What are the limitations of SqlDependency?

The most complete list I can find (from here) is as follows:

• The projected columns in the SELECT statement must be explicitly stated, and table names must be qualified with two-part names. Notice that this means that all tables referenced in the statement must be in the same database.
• The statement may not use the asterisk (*) or table_name.* syntax to specify columns.
• The statement may not use unnamed columns or duplicate column names.
• The statement must reference a base table.
• The statement must not reference tables with computed columns.
• The projected columns in the SELECT statement may not contain aggregate expressions unless the statement uses a GROUP BY expression. When a GROUP BY expression is provided, the select list may contain the aggregate functions COUNT_BIG() or SUM(). However, SUM() may not be specified for a nullable column. The statement may not specify HAVING, CUBE, or ROLLUP.
• A projected column in the SELECT statement that is used as a simple expression must not appear more than once.
• The statement must not include PIVOT or UNPIVOT operators.
• The statement must not include the UNION, INTERSECT, or EXCEPT operators.
• The statement must not reference a view.
• The statement must not contain any of the following: DISTINCT, COMPUTE or COMPUTE BY, or INTO.
• The statement must not reference server global variables (@@variable_name).
• The statement must not reference derived tables, temporary tables, or table variables.
• The statement must not reference tables or views from other databases or servers.
• The statement must not contain subqueries, outer joins, or self-joins.
• The statement must not reference the large object types: text, ntext, and image.
• The statement must not use the CONTAINS or FREETEXT full-text predicates.
• The statement must not use rowset functions, including OPENROWSET and OPENQUERY.
• The statement must not use any of the following aggregate functions: AVG, COUNT(*), MAX, MIN, STDEV, STDEVP, VAR, or VARP.
• The statement must not use any nondeterministic functions, including ranking and windowing functions.
• The statement must not contain user-defined aggregates.
• The statement must not reference system tables or views, including catalog views and dynamic management views.
• The statement must not include FOR BROWSE information.
• The statement must not reference a queue.
• The statement must not contain conditional statements that cannot change and cannot return results (for example, WHERE 1=0).
• The statement can not specify READPAST locking hint.
• The statement must not reference any Service Broker QUEUE.
• The statement must not reference synonyms.
• The statement must not have comparison or expression based on double/real data types.
• The statement must not use the TOP expression.

Additional reference:

• Working with Query Notifications

In addition to this, for anyone else thinking about using SqlDependency to receive notifications about changes, I've been using this approach in production, and I'm finding problems with it. I'm looking into it to see if the problems are related to my code, but the main issues are:

• If you fire multiple changes in quick succession, you don't always get the equivalent number of events coming through to the code. In my code, if 2 new records are inserted one after the other, I only get the one notification (for the last one).

• There is no way to know the record that was added. So if you add a new record, and the code fires to receive the notification, there is no way in the code to know the id of that new record, so you need to query the database for it.