Count unique values in a field of a table

[apestaart]

Hi,
I want to count the number of unique postcodes in a table.
So 1433 GS is in 3 other records aswell, but count as one.
I need this to calculate the number of books to distribute given the fact that I only distribute one book per postcode.

Hoe Can I write a SQL statement for that function?
Best regards,
Apestaart

 

[traingamer]

Among other ways:

SELECT Sum(cnt) AS SumOfcnt
FROM (SELECT posttable.postcode, 1 AS cnt
FROM posttable
GROUP BY posttable.postcode, 1)
;

where posttable is the name of your table and postcode is the name of your field.

Greg
"Personally, I am always ready to learn, although I do not always like being taught." - Winston Churchill

 

[PWise]

select count(*) from(
Select count(*) p
from posttable
GROUP BY posttable.postcode)p

No need to sum

 

[apestaart]

Hi,
Thank you so far. But what if I add a condition like Postcode > 1500AR?
How can I add that to the SQL statement?
Regards,
Apestaart

 

[PWise]

select count(*) from(
Select count(*) p
from posttable
Where Postcode > "1500AR"
GROUP BY posttable.postcode)p