[freetds] bcp, for browse and flags

Lowden, James K LowdenJK at bernstein.com
Tue Apr 29 11:00:28 EDT 2003


> From: ZIGLIO Frediano [mailto:Frediano.Ziglio at vodafoneomnitel.it]
> Sent: April 29, 2003 5:11 AM
> 
> I work a bit on column flags. Server send information from 
> column to client. I checked and updated these information including:
> - column is a key
> - column is writable
> - column is an identity
> - column is hidden
> - column is nullable

Yay! 

> CREATE TABLE table_name
> (
> 	id NUMERIC(10,0) IDENTITY PRIMARY KEY, -- I used 
> NUMERIC cause is more portable
> 	b VARCHAR(10) NULL,
> 	c INT NOT NULL
> )
> 
> And do a "SELECT c,b FROM table_name FOR BROWSE" 3 columns 
> are returned (TODO: do not show third column to client)
> c: not nullable and writable (nullable not returned from TDS4.2)
> b: nullable and writable (nullable not returned from TDS4.2)
> id: writable, identity, key, hidden (some db do not return 
> key for identity)
> 
> IMHO BCP should issue FOR BROWSE select and test if a column 
> is key and/or identity (these flags are valid in all version 
> of TDS). However I don't know how BCP should handle id/key 
> fields... set identity_insert on ??? do not insert these 
> field assuming db generate it (perhaps we lost foreign key) ??

BCP doesn't care about keys, and many times they're not declared: the old
style "create unique clustered index I on T(A,B)" has the same effect (and
lets A or B be null).  

You're right that freebcp will need to discover Identity columns.  Another
way to do that would be, "select colid, name from syscolumns where 0 <>
status & 0x80 and object_name(id) = '<tablename>'" will do the job on any
server afaik.  Not sure about ASA.  

In double checking this information, I came across this description for
syscolumns.status from Sybase:

Bits 0-2 (values 1, 2, and 4) indicate bit positioning if the column uses
the bit datatype. If the column uses the text/image datatype, bits 0 and 1
indicate replication status as follows:
    * 01 = always replicate
    * 10 = replicate only if changed
    * 00 = never replicate
Bit 3 (value 8) indicates whether NULL values are legal in this column.
Bit 4 (value 16) indicates whether more than one check constraint exists for
the column.
Bits 5 and 6 are used internally.
Bit 7 (value 128) indicates an identity column.
Bit 8 is unused.

Poor Bit 8 must be feeling a bit crowded, don't you think?  

--jkl

http://sybooks.sybase.com/onlinebooks/group-as/asg1250e/refman/@Generic__Boo
kTextView/135819;pt=129523/*?DwebQuery=syscolumns&DwebSearchAll=1#X



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