Question

I have a table like this

IDX       IDY   ColX ColY ...
------------------------------
idx1      idy1
idx1      idy1
idx1      idy1
idx2      idy4
idx2      idy4
idx3      idy1
idx3      idy1
idx3      idy1
idx3      idy1
...       ...
...       ...

So for each unique IDX there is one IDY. I need the count of IDYs across unique IDXs.
ie., I need

Count       IDY
---------------
2           idy1 (1 for idx1s and 1 for idx3s)
1           idy4 (1 for idx2s)
...

Can I do this in one query ? How ?

Answer 1

SELECT
    IDY, Count(DISTINCT IDX) As IDXCount
FROM
    TableName
Group BY
    IDY