Hi, Steven, Thanks for you interest in FastBit. There is no '\N' in FastBit. Null values are recorded using a separate bit vector. If you create a FastBit data partition from a CSV file, a value is treated as null if the corresponding position is left blank. If you use ibis::tablex to generate a data partition, then unspecified values are treated as NULL.
The NULL values are never outputted through ibis.cpp and others in the examples directory. In the query expressions, the only way to talk about NULL is the "NOT NULL" operator. This operator is used as follows column_name NOT NULL The only way to say you only want to see rows with only NULL values for a particular column is (NOT column_name NOT NULL). This is intentionally complicated because we intend to discourage such uses. Hope this helps. John PS: here is a link to an earlier discussion thread about NULL values https://hpcrdm.lbl.gov/pipermail/fastbit-users/2009-December/000511.html On 1/13/15 1:51 AM, wang jilong wrote: > Hi John, > > Question 1: If a column contains NULL values, is it stored as '\N'? > Question 2: For NULL values, to filter using sql, should it look like colname > = '\N'? > > Thanks > > Steven Wang > > _______________________________________________ > 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
