|
|
Posted by Yas on 08/18/07 21:45
On 18 Aug, 22:14, Erland Sommarskog <esq...@sommarskog.se> wrote:
> Yas (yas...@gmail.com) writes:
> > Hi, is there a way I can check if a table is empty and contains no
> > rows?
>
> > I have a Table1 which being dynamic can sometimes end up with now
> > columns what so ever. I'm using Table1 in one of my views along with 2
> > other tables and I would like put a condition at the...something like
> > AND Table1 IS NOTEMPTY
>
> AND EXISTS (SELECT * FROM Table1)
>
> The EXISTS / NOT EXISTS are part of the essential SQL anyone who is
> working with SQL should learn. The above example is simple, but say
> you want all customers who have placed an order / who have never placed
> an order:
>
> SELECT C.CustomerID, C.CompanyName
> FROM Customers C
> WHERE /* NOT */ EXISTS (SELECT *
> FROM Orders O
> WHERE O.CustomerID = C.CustomerID)
>
> You may be used to using IN / NOT IN for this, but (NOT) IN is limited,
> as you get problem if you have a multi-column key. Plus that NOT IN
> can trap you if NULL values are involved.
>
> The query above runs in the Northwind database, if you want to try it.
Oh that's good, thanks! :-)
....and if I wanted to say make sure in a table where normaly there
should be 2000 rows, there are at least 1500 present could I just
simply do the following...or is there a better way?
AND ((SELECT COUNT(*) FROM TABLE1) > 1500)
what do you think of that?
Cheers
Yas
Navigation:
[Reply to this message]
|