摘要:
-聚合函数 (1)count(*)求个数 (2)avg(*)求平均数 (3)max(*)求最大值 (4)min(*)求最小值 (5)sum(*)求和 (1)select(select COUNT(*) from student where sex='男'and classcode='20050102... 阅读全文
摘要:
select*from category where Parent='011'or'012'or'013' select*from Category where Parent not in('011','012','013')--parent不是012,013,011的 select*from Ca... 阅读全文