如何计算 SQL 中连接表上的行数？

Question

I'm trying to do a join on two tables and count the rows of the second one as they are an event themselves. Here is the code, I've tried a subquery, but I'm not sure if the is the right approach:

SELECT
    a.E_PST_DATE,
    case when unfilled = 'true' then 'unfilled' else a.bidder end  bidder, 
    a.browser,
    a.site_name,
    a.placement,
    a.device_name, 
    b.PAGENUMBER,
    (SUM(a.CPM)/1000) revenue,
    COUNT(a.sessiontoken) impressions,
    COUNT(b.*) page_views
FROM Table1 a
LEFT JOIN Table2 b ON a.SESSIONTOKEN = b.SESSIONTOKEN
    AND a.SESSIONDEPTH = b.SESSIONDEPTH AND b.PST_DATE > current_date - 3 
WHERE a.E_PST_DATE > current_date - 3 AND b.PAGENUMBER IS NOT NULL
GROUP BY 1, 2, 3, 4, 5, 6, 7

Answer 1

Insteas of COUNT(b. ) page_views Please any not null column name. count( ) might give you wrong answer

count(b.id)