Suppose I have a view defined as the union of multiple table queries e.g.
create view v1 as SELECT col1 as a , col2 as b FROM table1 UNION SELECT col2 as a , col3 as b FROM table2 UNION SELECT col4 as a , col5 as b from table 3; If I use this view in a query ... select * from v1 where a=5 ... what is the behavior of applying the where condition into the view. From what I can tell, it seems to be running each unconditioned SELECT without a where clause and then filtering the actual results that than applying the where clause into the individual SELECTs of the union ... e.g. SELECT col1 as a , col2 as b FROM table1 where col1=5 UNION SELECT col2 as a , col3 as b FROM table2 where col2=5 UNION SELECT col4 as a , col5 as b from table3 where col4=5 I need to verify that this is not due to out of data statistics (I do not think that is the case) but I felt it was probably worth finding out whether I am being a little too optimistic on what the planner can do. Thanks, Jeff -- View this message in context: http://apache-database.10148.n7.nabble.com/How-does-WHERE-condition-in-a-VIEW-with-UNIONs-get-applied-tp133834.html Sent from the Apache Derby Users mailing list archive at Nabble.com.
