摘要：
(1).CAST()函数的参数是一个表达式，它包括用AS关键字分隔的源值和目标数据类型。以下例子用于将文本字符串'12'转换为整型:SELECT CAST('12' AS int)(2).返回值是整型值12。如果试图将一个代表小数的字符串转换为整型值，又会出现什么情况呢？SELECT CAST('12.5' AS int)(3).CAST()函数和CONVERT()函数都不能执行四舍五入或截断操作。由于12.5不能用int数据类型来表示，所以对这个函数调用将产生一个错误:Server: Msg 245, Level 16, State 1, Li 阅读全文
摘要：
select * from Studentselect * from ClassFormselect [Name],ClassName from Student as a left join ClassForm as b on a.ClassID=b.IDselect [Name],ClassName from Student as a right join ClassForm as b on a.ClassID=b.IDselect [Name],ClassName from Student as a inner join ClassForm as b on a.ClassID=b.IDse 阅读全文