select sum(portal_count)portal_count from a,b where a.websiteid = b.websiteid and b.datetime >= '2014-10-15' and b.datetime < '2014-10-16'
SELECT t1.*,SUM(t2.portal_count) FROM 表1 AS t1 LEFT JOIN 表2 AS t2 ON t1.websiteid = t2.websiteid WHERE t2.datetime BETWEEN '2014-10-15 00:00:00' AND '2014-10-15 23:59:59' GROUP t1.websiteid试试这个呢,这里的“表1”、“表2”需要替换成你数据库中的表名
FROM 表1 AS t1
LEFT JOIN 表2 AS t2 ON t1.websiteid = t2.websiteid
WHERE t2.datetime BETWEEN '2014-10-15 00:00:00' AND '2014-10-15 23:59:59'
GROUP t1.websiteid试试这个呢,这里的“表1”、“表2”需要替换成你数据库中的表名
不行啊 如果表t1中在表t2中没有相关数据 where条件会把表t1的不相关数据过滤掉