如何在PostgreSQL中制定条件和？

Question

我的表格包含id，category，noofquestions和company。我想要一个查询，当noofquestions在两列或更多列中相同时，noofquestions的值为category的总和。我正在尝试此查询，但它只添加类别相同且noofquestions相等且错误的列。它不应该检查noofquestions。

 SELECT id ,  category,   SUM(NULLIF(noofquestions, '')::int), company 
 FROM tableName   
 WHERE id=1 
 GROUP BY id, category, noofquestions, company;

Answer 1

您不应按noofquestions分组：

SELECT   id, category, SUM(NULLIF(noofquestions, '')::int), company 
FROM     tableName 
WHERE    id = 1 
GROUP BY id, category, company;