I am trying to find the Chi-Square test from my following SQL Server Query on the sample data:
SELECT sessionnumber, sessioncount, timespent, expected, dev, dev*dev/expected as chi_square
FROM (SELECT clusters.sessionnumber, clusters.sessioncount, clusters.timespent,
(dim1.cnt * dim2.cnt * dim3.cnt)/(dimall.cnt*dimall.cnt) as expected,
clusters.cnt-(dim1.cnt * dim2.cnt * dim3.cnt)/(dimall.cnt*dimall.cnt) as dev
FROM clusters JOIN
(SELECT sessionnumber, SUM(cnt) as cnt FROM clusters
GROUP BY sessionnumber) dim1 ON clusters.sessionnumber = dim1.sessionnumber JOIN
(SELECT sessioncount, SUM(cnt) as cnt FROM clusters
GROUP BY sessioncount) dim2 ON clusters.sessioncount = dim2.sessioncount JOIN
(SELECT timespent, SUM(cnt) as cnt FROM clusters
GROUP BY timespent) dim3 ON clusters.timespent = dim3.timespent CROSS JOIN
(SELECT SUM(cnt) as cnt FROM clusters) dimall) a
My table has this sort of sample data:
sessionnumber sessioncount timespent cnt
1 17 28 NULL
2 22 8 NULL
3 1 1 NULL
4 1 1 NULL
5 8 111 NULL
6 8 65 NULL
7 11 5 NULL
8 1 1 NULL
9 62 64 NULL
10 6 42 NULL
The problem is that this query works fine but it gives wrong output or you can say no output at all. The output it gives my is like:
sessionnumber sessioncount timespent expected dev chi_square
1 17 28 NULL NULL NUL
2 22 8 NULL NULL NULL
3 1 1 NULL NULL NULL
4 1 1 NULL NULL NULL
5 8 111 NULL NULL NULL
6 8 65 NULL NULL NULL
7 11 5 NULL NULL NULL
8 1 1 NULL NULL NULL
9 62 64 NULL NULL NULL
10 6 42 NULL NULL NULL
How can I get rid of this problem because I tried my best at all! Thanks in advance telling me what I' doing wrong!
In your sample data, cnt is NULL, so the results are also NULL. You can replace these NULL values with a default value (1 for example, I don't know what is the context) using ISNULL, like
SELECT sessionnumber, SUM(ISNULL(cnt, 1)) as cnt FROM clusters GROUP BY sessionnumber
来源：https://stackoverflow.com/questions/18014961/sql-server-query-to-find-chi-square-values-not-working