Combine the results of two or more select statements.
[ UNION [ ALL | DISTINCT ] select-statement-without-ordering ]...
[ ORDER BY [ number [ ASC | DESC ] , ... ]
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. UNION DISTINCT is identical to UNION.
If corresponding items in two select lists have different data types, UltraLite chooses a data type for the corresponding column in the result and automatically converts the columns in each component SELECT statement appropriately.
The column names displayed are the same column names that are displayed for the first SELECT statement. An alternative way of customizing result set column names is to use the WITH clause in the SELECT statement.
The ORDER BY clause uses integers to establish the ordering, where the integer indicates the query expression(s) on which to sort the results.
The following example lists all distinct surnames of employees and customers.
SELECT emp_lname FROM Employee UNION SELECT lname FROM Customer