我正在尝试将空值显示为零，如何将这些表连接在一起？

Question

这是我所拥有的查询，据我所知，它应该是正确的，除了我不确定如何使用建筑物作为公共字段组合表。

SELECT l.building AS "BUILD", NVL(NUMSECTIONS, 0) AS "NUMSECTIONS"
FROM location l
LEFT OUTER JOIN 
(SELECT building AS "BUILD", COUNT(*) AS "NUMSECTIONS"
FROM location l
INNER JOIN sections e
ON l.locationid = e.locationid
INNER JOIN courses c
ON e.courseid = c.courseid
WHERE subjectcode IN ('CS', 'NET', 'WEB', 'MATH', 'ENGL', 'HIST', 'ZOOL', 'ART', 'COMM', 'BSAD')
GROUP BY building)s
ON l.building = s.building

将内部表中的building赋值为s.building似乎不起作用，因为我需要它

Answer 1

如果你的查询抛出一个错误，s.building不存在，这肯定是因为在你的子查询中，building列被别名为'BUILD'，所以你应该加入l.building和s."BUILD"