目录包装类装箱拆箱类型转换IntegerCharacter判断转化StringStringString BufferStringBuilder区别FileFile创建修改判断获取自定义获取文件名排序Date集合ArrayArrayListLinkListHashSetHashMapQueue工具类ObjectReflection 反射PropertiesClassConstructorFieldMethod 包装类
INSERT INTO student VALUES(1,'蔺斐','男','2002-04-09',0.25);INSERT INTO student VALUES(2,'熊大','男','1999-08-08',100);INSERT INTO student VALUES(3,'吉吉国王','男','2009-09-09'
-- 查询时合并列 只针对数值类型字段-- 查询每个同学三门课总成绩-- 数值类型之间可以进行+—%*SELECT sname,html+css+js AS 总成绩 FROM score; SELECT sname,js FROM score WHERE js>=60;-- 查询js成绩及格同学姓名、js成绩。 SELECT * FROM score WHERE js>=50 AND js<=90;--
