Reference Manual
CHAPTER 9. SQL Statements
To combine the results of two or more select statements.
select-without-order-by
... UNION [ALL] select-without-order-by
... [ UNION [ALL] select-without-order-by ] ...
... [ ORDER BY integer [ ASC | DESC ], ... ]
Must have SELECT permission for each of the component SELECT statements.
None.
The results of several SELECT statements can be combined into a larger result using UNION. The component SELECT statements must each have the same number of items in the select list, and cannot contain an ORDER BY clause.
The results of UNION ALL are the combined results of the component SELECT statements. The results of UNION are the same as UNION ALL except that duplicate rows are eliminated. Eliminating duplicates requires extra processing, so UNION ALL should be used instead of UNION where possible.
If corresponding items in two select lists have different data types, Adaptive Server Anywhere will choose a data type for the corresponding column in the result and automatically convert the columns in each component SELECT statement appropriately.
If ORDER BY is used, only integers are allowed in the order by list. These integers specify the position of the columns to be sorted.
The column names displayed are the same column names which would be displayed for the first SELECT statement.
SQL/92 Entry level.
Sybase Supported by Adaptive Server Enterprise, which also supports a COMPUTE clause.
List all distinct surnames of employees and customers.
SELECT emp_lname FROM Employee UNION SELECT lname FROM Customer