Question

table >>> sales

state | date | item | px

101   1/1/2012   tennis   2
101   1/1/2012   soccer   10
101   1/1/2012   crystal  100
101   1/1/2012   soccer   10

102   1/1/2012   crystal  100
102   1/1/2012   tennis   2
102   1/2/2012   tennis   2

103   1/2/2012   tennis   2
103   1/2/2012   crystal  100
103   1/3/2012   soccer   10
103   1/3/2012   crystal  100


$query="SELECT state, MAX(date), COUNT(state), AVG(px) FROM sales GROUP BY state ORDER by state ASC";

… produces:

state | date | item count | avg px

101   1/1/2012   4   30.5
102   1/2/2012   3   34.67
103   1/3/2012   4   53

Question: How can the query be modified to produce the average px of DISTINCT items in each state? (Instead of the average px of ALL items in each state)

E.g., the average for state 101 should/would be (2+10+100)/3 = 37.33; i.e., the average px for 1 tennis, 1 soccer and 1 crystal.

08-04-12 EDIT >>> Changed px column header in second table to avg px. / edited for clarity. thx.

Answer 1

Give this a try.

EDIT: Added an inner query to distinct based on the item and state.

SELECT
    state,
    CONVERT(DATETIME, AVG(AverageDate)) AS AverageDate,
    SUM(ItemCount) AS [item count],
    AVG(px) AS px
FROM
(
    SELECT
        state,
        item,
        COUNT(*) AS ItemCount,
        AVG(CAST(date AS INT)) AS AverageDate,
        AVG(px) AS px
    FROM sales
    GROUP BY
        state,
        item
)
GROUP BY state;