Conditional INSERT

Hello,

I'm trying to perform an INSERT .. but only if no rows in the table
have a specific field that equals zero.

For example:

Nodes has the fields NodeID and ParentNodeID (there are more than
that, but this is simplified)

NodeID will be unique no matter what, since it is incremental.

I want to
INSERT INTO Nodes
VALUES(NULL, 0)

only if
// There are no Nodes that have a ParentNodeID of 0
SELECT COUNT(NodeID)
FROM Nodes
WHERE ParentNodeID = 0 is less than 1

Thank you

On Jun 25, 2:19 pm, evanp...@gmail.com wrote:
> Hello,
>
> I'm trying to perform an INSERT .. but only if no rows in the table
> have a specific field that equals zero.
>
> For example:
>
> Nodes has the fields NodeID and ParentNodeID (there are more than
> that, but this is simplified)
>
> NodeID will be unique no matter what, since it is incremental.
>
> I want to
> INSERT INTO Nodes
> VALUES(NULL, 0)
>
> only if
> // There are no Nodes that have a ParentNodeID of 0
> SELECT COUNT(NodeID)
> FROM Nodes
> WHERE ParentNodeID = 0 is less than 1
>
> Thank you

if not exists (select 1 from nodes where ParentNodeID = 0) begin
insert into Nodes
values(null, 0);
end if;

Unfortunately, that doesn't seem to be working for me.

I get a sytax error near

"if not exists (select 1 from nodes where ParentNodeID = 0) be"