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vc++ ado NULL

Posted on 2002-04-29
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Last Modified: 2010-04-02
I have worked in  VB 6.0 ADO ,there i found a method ISNULL to check a field item is null or not.
I am currently in VC++ 6.0 Ado, i am not able to find such a method . How could i test a field is
null.
0
Comment
Question by:v_iyengar
  • 13
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  • +2
26 Comments
 
LVL 30

Expert Comment

by:Axter
ID: 6976884
if (ptr == NULL)
{
}
0
 

Author Comment

by:v_iyengar
ID: 6976895
i want to check if Fields->GetItem(0l)->Value is null
0
 
LVL 30

Expert Comment

by:Axter
ID: 6976899
if (Fields->GetItem(0l)->Value == NULL)
{
}
0
 
LVL 30

Expert Comment

by:Axter
ID: 6976900
If you want to check if the return value of GetItem is null then you can do the following:
if (Fields->GetItem(0l)== NULL)
{
}
0
 
LVL 30

Expert Comment

by:Axter
ID: 6976903
If Value is a non-pointer, then I think what you're looking for is something like this.

if (Fields->GetItem(0l)== NULL)
{
  MyValue = Fields->GetItem(0l)->Value;
}
0
 
LVL 30

Expert Comment

by:Axter
ID: 6976905
Oops!  Correction:
if (Fields->GetItem(0l) != NULL)
{
 MyValue = Fields->GetItem(0l)->Value;
}
0
 

Author Comment

by:v_iyengar
ID: 6976948
i want to check with database null
0
 
LVL 30

Expert Comment

by:Axter
ID: 6976956
>>i want to check with database null
What do you mean?

What ever you have as a pointer, should be checked to see if the value equals to NULL.
0
 

Author Comment

by:v_iyengar
ID: 6976964
the value for an item in database can be NULL.
How can i check its null
Fields->GetItem(0l)->Value is a VARIANT ,how can i compare a VARIANT and NULL
0
 
LVL 3

Expert Comment

by:GGRUNDY
ID: 6976968
I think in the case of a NULLable charater field the variant type returned will be of type VT_NULL if the field is NULL.
0
 

Author Comment

by:v_iyengar
ID: 6976969
the value for an item in database can be NULL.
How can i check its null
Fields->GetItem(0l)->Value is a VARIANT ,how can i compare a VARIANT and NULL
0
 

Author Comment

by:v_iyengar
ID: 6976975
the value for an item in database can be NULL.
How can i check its null
Fields->GetItem(0l)->Value is a VARIANT ,how can i compare a VARIANT and NULL
0
 

Author Comment

by:v_iyengar
ID: 6976981
the value for an item in database can be NULL.
How can i check its null
Fields->GetItem(0l)->Value is a VARIANT ,how can i compare a VARIANT and NULL
0
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Author Comment

by:v_iyengar
ID: 6976987
yes vt type is set to VT_NULL
But will all database will do the same,set VT to VT_NULL or i have to check some other code like scode
0
 

Author Comment

by:v_iyengar
ID: 6976997
yes vt type is set to VT_NULL
But will all database will do the same,set VT to VT_NULL or i have to check some other code like scode
0
 

Author Comment

by:v_iyengar
ID: 6977029
yes vt type is set to VT_NULL
But will all database will do the same,set VT to VT_NULL or i have to check some other code like scode
0
 
LVL 3

Expert Comment

by:GGRUNDY
ID: 6977092
Sorry but after lots of ploughing through documentation I can't find anything which gives me confidence that comparing against VT_NULL will be reliable in all weather. But I'm guessing it will probably be as reliable as your original VB test was.
0
 

Author Comment

by:v_iyengar
ID: 6977363
yes vt type is set to VT_NULL
But will all database will do the same,set VT to VT_NULL or i have to check some other code like scode
0
 

Author Comment

by:v_iyengar
ID: 6977374
so you mean ISNULL in vb only test for VT=VT_NULL
0
 
LVL 3

Expert Comment

by:GGRUNDY
ID: 6978558
As VB uses a variant type internally that is my suspicion.
0
 

Author Comment

by:v_iyengar
ID: 6979518
so u mean to say its enough if i check VT=VT_NULL ?
0
 
LVL 3

Accepted Solution

by:
GGRUNDY earned 25 total points
ID: 6979759
No ....
I mean that's what "I" would do x.vt == VT_NULL,
but I would do it without great confidence because the
documentation is really crappy.
0
 
LVL 6

Expert Comment

by:Mindphaser
ID: 7036271
Please update and finalize this old, open question. Please:

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0
 

Author Comment

by:v_iyengar
ID: 7040973
i am also doing the same,but i do not know is it correct?
0
 
LVL 11

Expert Comment

by:griessh
ID: 7122187
I suggest to split between Axter and GGRUNDY

======
Werner
0
 
LVL 6

Expert Comment

by:Mindphaser
ID: 7138107
Force accepted

** Mindphaser - Community Support Moderator **

Axter, there will be a separate question with points for your help.
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