This is an Access Update query and subquery.
There is a table called [zControl Entries]. It is supposed contains various other tables' total records. Therefore one entry in this table [zControl Entries] is called [Item Master], and this table [Item Master] is another table also, whose records are to be stored here in [zControl Entries].
Therefore I fire a query, and get an error 'Operation must use an updatable query'. Following is my query.
UPDATE [zControl Entries] As Ce
SET Ce.NumericValue = (Select Count(*) As NumericValue From [Item Master])
Where Ce.EntityType='Item Master'
Here 'Item Master' is a value in Ce table, whereas [Item Master] is also a physical table in the same database.