Queries using set operations
Used to bring together in one result set data from two or more unrelated
tables or queries that have identical structure (same number of columns with
same data types occurring in the same order; not necessarily same column
headers).
A UNION
query cannot be built in the graphical query interface in Access.
Example
Customers and Suppliers by City
- Variable number of SELECT statements linked by the key
word
- Columns must be named (important if they were calculated)
- Optional additional column or columns to add information
or to make table structures match
- No duplicates unless UNION ALL is specified (not obvious
from this example)
- If the result set is to be sorted, only one ORDER BY
clause at the end