Combines 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 ] [, …] ]
Lists all distinct surnames of employees and customers:
SELECT Surname FROM Employees UNION SELECT Surname FROM Customers
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. See “FROM 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, Sybase IQ chooses a data type for the corresponding column in the result, and automatically converts 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 that display for the first SELECT statement.
When SELECT statements include constant
values and UNION ALL views but omit the FROM clause,
use iq_dummy to avoid errors. See “FROM clause” for details.
None
Must have SELECT permission for each of the component SELECT statements.
