Two rows are duplicates of one another only if each value in the first row is equal to the corresponding value of the second row.
A UNION eliminates all but one row of each set of duplicates. The number of rows in the UNION table is the sum of the number of rows in R1 and R2, less the number of duplicates eliminated.
If ALL is specified, duplicate rows are not eliminated.
|
Copyright © 2014 CA.
All rights reserved.
|
|