Rock, To complement what John is saying, i found a very special corner case where you can actually test for NULL. In category columns, NULL is always a special key 0, and it seems that testing a category column against a key does what you would expect. So to test NULL or NOT NULL values, i simply does col=0 or col!=0.
John, can you confirm this behavior ? Thanks, -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John Wu Sent: Monday, January 30, 2012 4:53 PM To: Rock Wang; FastBit Users Subject: Re: [FastBit-users] how to handle empty column Hi, Rock, Null values for each individual column is marked with a mask for the column. An entire row may be marked as unusable, with a partition-wide mask. At the moment, NULL values can not be queried or printed. Therefore, if you want to use NULL values to express something definitely, you should consider a special code in your own database design because you can not rely on the fact FastBit to query NULL values. For example, "a = NULL" or "a != NULL" are not supported. If you enter these expressions, FastBit will interpret "NULL" to be a column name -- definitely not want you want. Inside FastBit, if name a column in either the where clause or the select clause, the null mask for the column is checked to make sure the rows returned do not contain any NULL values. Hope this helps. John On 1/30/12 1:00 PM, Rock Wang wrote: > Hi John > > How does empty or null column is handled in fastbit? do you have examples? > > Thanks, > Rock _______________________________________________ FastBit-users mailing list [email protected] https://hpcrdm.lbl.gov/cgi-bin/mailman/listinfo/fastbit-users _______________________________________________ FastBit-users mailing list [email protected] https://hpcrdm.lbl.gov/cgi-bin/mailman/listinfo/fastbit-users
