Without an example I can only offer general advice. In order to get a count from each table, you'll need to query each table individually. However, you can combine the output. One mechanism would be to use a [UNION query]. :
You could create a view over the two tables and query that for the rowcount... Assuming the tables have compatible fields (or you can make an appropriate subset of fields). eg: CREATE VIEW MyView AS SELECT ID, Field1, Field2, CreatedDate FROM Table1 UNION SELECT ID, Field3 AS Field1, Field4 AS Field2, CreatedDate FROM Table2 and then SELECT COUNT(*) FROM MyView WHERE CreatedDate >= '2013-01-01' AND CreatedDate
Grant and Thomas answers are correct, but you need to use UNION ALL to get all records from both tables, otherwise you'll get only distinct records. UNION is often abused where UNION ALL can be used to increase performance.
There are multiple ways to do this. You can UNION the two tables together and do the condition on that if you're looking for a single answer. Another method, if you're looking for a comparison is to use sub-queries. SELECT (SELECT COUNT(*) FROM TableA WHERE Condition) TableA, (SELECT COUNT(*) FROM TableB WHERE Condition) TableB