sql-學習筆記1

NULL AS：select出來一個虛列並且用null填充 ISNULL(X字段,0)：如果「X字段」爲空就把他變成0 where Address IS NULL：Address爲空的條件 sum(case when s_id=1 then p_num else 0 end) as s1_id 

>>阅读原文<<