SQL语句的执行顺序 SELECT 语句的处理顺序。 1.FROM 2.ON 3.JOIN 4.WHERE 5.GROUP BY 6.WITH CUBE 或 WITH ROLLUP 7.HAVING 8.SELECT 9.DISTINCT 10.ORDER BY 11.TOP 类型转换函数和union CAST ( expression AS data_type) CONVERT ( data_type, expression,
SQL语句的执行顺序
SELECT 语句的处理顺序。
1.FROM
2.ON
3.JOIN
4.WHERE
5.GROUP BY
6.WITH CUBE 或 WITH ROLLUP
7.HAVING
8.SELECT
9.DISTINCT
10.ORDER BY
11.TOP
类型转换函数和union
CAST ( expression AS data_type)
CONVERT ( data_type, expression,[style])
Select ‘您的班级编号’ 1 错误这里 是数学运算符
SELECT FIdNumber,
CAST(RIGHT(sNo,3) AS int) as 后三位的整数形式,
CAST(RIGHT(sNo,3) AS int) 1 as 后三位加1,
CONVERT(int,RIGHT(sNo,3))/2 as 后三位除以2
FROM student
select fname,LEN(FName) as '名字的长度' from MyStudent
--CAST ( 要转换的数据/字段AS 目标数据类型)
select
cast(ISNULL(fmath,0) as varchar(10))
cast(ISNULL(fenglish,0) as varchar(10))
from MyStudent
select cast(1 as varchar(10)) cast(1 as varchar(10))
--CONVERT ( 目标数据类型, 待转的数据或字段)
select Convert(varchar(10),1) Convert(varchar(10),1)
select * from MyStudent
select Convert(varchar(10),fage) fgender from MyStudent
select CONVERT(varchar(20), getdate(),23)
--union联合后会删除相同内容的行,union all不会
--union 1)列数相同 2)对应列的类型相同
select * from newStudent union all
select * from newStudent2
--显示班级的数学和英语成绩，，以及总成绩？
select fname,fmath,fenglish from newStudent
union all
select '总分：',sum(fmath),sum(fenglish) from newStudent
select 1,80,100 union all
select 1,80,100 union
select 3,50,59 union all
select 4,66,89 union
select 5,59,100
存储过程（procedure）
