What is the main difference between a UNION statement and a UNION ALL statement? 1. A UNION statement eliminates duplicate rows; a UNION ALL statement includes duplicate rows. 2. A UNION statement can be used to combine any number of queries; a UNION ALL statement can be used to combine a maximum of two queries. 3. A UNION statement can only combine queries that have parallel fields in the SELECT list; a UNION ALL statement can combine queries with differing SELECT list structures. 4. A UNION statement cannot be used with aggregate functions; a UNION ALL statement can be used with aggregate functions. 5. There is no difference between the two statements; they are interchangeable.

2 Answers   Saman Bank, Sonata,

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consider a table which contain 4 columns,ename,eno,sal and deptno, from this table i want to know ename who having maximum salary in deptno 10 and 20.

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