SQL Server高级内容之表表达式和复习 1 ． 表表达式 (1)将表作为一个源或将查询的一个结果集作为一个源，对源做处理，然后得到一个新的数据源，对其进行查询。 (2) (3)派生表，将表的查询得到的结果集作为一个新的数据源，需要注意一下几点： 1) 派生表必须
SQL Server高级内容之表表达式和复习
1． 表表达式
(1) 将表作为一个源或将查询的一个结果集作为一个源，对源做处理，然后得到一个新的数据源，香港服务器，服务器空间，对其进行查询。
(2)
(3)派生表，香港虚拟主机，将表的查询得到的结果集作为一个新的数据源，需要注意一下几点：
1)派生表必须有括号括起。
2)派生表需要取别名
3)派生表中的所有字段也要有别名
4)能够作为派生表的只有结果集（游标不行）。
(4)
( s1.stuID, 6 7 s1.stuName, s1.stuSex stuSex, (yy,s1.stuBirthdate,getdate()) as stuAge, (varchar(10),s1.stuStudyDate,101) as stuStudyDate, 20 21 s1.stuEmail, 22 23 s1.stuPhone, 24 25 s2.testBase, 26 27 s2.testBeyond, 28 29 s2.testName, (varchar(10),s2.testDate,101) as testDate, 32 33 s3.className, 34 35 s3.classDescription Student as s1 Score as s2 s1.stuID=s2.stuID Course as s3 s1.classID=s3.classID s1.stuIsDel) as tb1 tb1.stuAgetb1.stuSex
2． SQLHelper的一些知识点
(1) SqlConnection用来连接数据库
(2)SqlCommand用来执行SQL语句
1)参数化查询： SqlParameter
2)执行方法
->ExecuteNonQuery() 执行增删改，返回首影响的行数
->ExecuteScalar()
->ExecuteReader() 返回DataReader
(3)SqlDataReader用来读取每一条数据
(4) SqlDataAdapter封装了以上的所有的类
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