第十二单元 `T-SQL` 编程

刘修利 · 发表于 2023-12-19 20:02:23

create database step2_unit12;
go
use step2_unit12;
go
-- 部门表
CREATE TABLE [dbo].[Department](
[Id] [int] PRIMARY KEY IDENTITY(1,1) NOT NULL,
[Name] [varchar](20) NULL
);
-- 职位表
CREATE TABLE [dbo].[Job](
[Id] [int] PRIMARY KEY IDENTITY(1,1) NOT NULL,
[Name] [varchar](20) NULL
);
-- 人员表
CREATE TABLE [dbo].[person](
[Id] [int] PRIMARY KEY IDENTITY(1,1) NOT NULL,
[Name] [varchar](50) NULL,
[Sex] [varchar](10) NULL,
[Age] [int] NULL
);
-- 工资表
CREATE TABLE [dbo].[Salary](
[Id] [int] PRIMARY KEY IDENTITY(1,1) NOT NULL,
[Sal] [money] NULL,
[Comm] [money] NULL,
[StaffId] [int] NULL
);
-- 员工表
CREATE TABLE [dbo].[Staff](
[Id] [int] PRIMARY KEY IDENTITY(1,1) NOT NULL,
[Name] [varchar](20) NOT NULL,
[Hiredate] [datetime] NOT NULL,
[DepartmentId] [int] NULL,
[JobId] [int] NULL
);
SET IDENTITY_INSERT [dbo].[Department] ON
INSERT [dbo].[Department] ([Id], [Name]) VALUES (1, N'技术部')
INSERT [dbo].[Department] ([Id], [Name]) VALUES (2, N'人资部')
INSERT [dbo].[Department] ([Id], [Name]) VALUES (3, N'市场部')
SET IDENTITY_INSERT [dbo].[Department] OFF
SET IDENTITY_INSERT [dbo].[Job] ON
INSERT [dbo].[Job] ([Id], [Name]) VALUES (1, N'经理')
INSERT [dbo].[Job] ([Id], [Name]) VALUES (2, N'组长')
INSERT [dbo].[Job] ([Id], [Name]) VALUES (3, N'员工')
SET IDENTITY_INSERT [dbo].[Job] OFF
SET IDENTITY_INSERT [dbo].[person] ON
INSERT [dbo].[person] ([Id], [Name], [Sex], [Age]) VALUES (1, N'高圆圆', N'女', 28)
INSERT [dbo].[person] ([Id], [Name], [Sex], [Age]) VALUES (2, N'王佳佳', N'女', 32)
INSERT [dbo].[person] ([Id], [Name], [Sex], [Age]) VALUES (3, N'杨硕', N'男', 25)
SET IDENTITY_INSERT [dbo].[person] OFF
SET IDENTITY_INSERT [dbo].[Salary] ON
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (1, 15000.0000, 10000.0000, 1)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (2, 15000.0000, 9000.0000, 2)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (3, 12000.0000, 8000.0000, 3)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (4, 8000.0000, 6000.0000, 4)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (5, 4000.0000, 3000.0000, 5)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (6, 9000.0000, 8000.0000, 6)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (7, 15000.0000, 12000.0000, 7)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (8, 12000.0000, 9000.0000, 7)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (9, 7000.0000, 2000.0000, 9)
INSERT [dbo].[Salary] ([Id], [Sal], [Comm], [StaffId]) VALUES (10, 9000.0000, 8000.0000, 10)
SET IDENTITY_INSERT [dbo].[Salary] OFF
SET IDENTITY_INSERT [dbo].[Staff] ON
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (1, N'王鑫', CAST(N'2014-02-01 00:00:00.000' AS DateTime), 1, 1)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (2, N'张磊', CAST(N'2015-09-03 00:00:00.000' AS DateTime), 2, 1)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (3, N'李鹏', CAST(N'2016-08-01 00:00:00.000' AS DateTime), 3, 2)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (4, N'王洋', CAST(N'2019-02-03 00:00:00.000' AS DateTime), 1, 3)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (5, N'吴潘', CAST(N'2018-10-01 00:00:00.000' AS DateTime), 2, 3)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (6, N'贾丹', CAST(N'2018-07-01 00:00:00.000' AS DateTime), 2, 2)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (7, N'李露', CAST(N'2016-09-01 00:00:00.000' AS DateTime), 3, 1)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (8, N'杨腾', CAST(N'2018-11-08 00:00:00.000' AS DateTime), 1, 2)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (9, N'孙艺', CAST(N'2018-12-26 00:00:00.000' AS DateTime), 3, 3)
INSERT [dbo].[Staff] ([Id], [Name], [Hiredate], [DepartmentId], [JobId]) VALUES (10, N'赵帅', CAST(N'2019-01-03 00:00:00.000' AS DateTime), 1, 3)
SET IDENTITY_INSERT [dbo].[Staff] OFF

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1. T-SQL 命名规则

1，开头不能是数字，空格或特殊字符
2，首字符后可以包含字母数字汉字 _ @ #
3，不能是系统保留字（关键字）

2. 变量

全局变量

整个系统都可以使用

@@ERROR 返回执行的上一个T-SQL语句的错误号,0 代表没有错误，非0 代表有错误
begin tran
declare @a int = 1;
select @a/0
select @@ERROR
commit
@@IDENTITY 返回插入到表的IDENTITY列的最后一个值
@@LANGUAGE返回当前所用语言的名称
@@MAX_CONNECTIONS返回Sql Server实例允许同时进行的最大用户连接数
@@ROWCOUNT返回上一次语句影响的数据行的行数
@@SERVERNAME返回运行Sql Server的本地服务器的名称
@@SERVICENAME返回Sql Server正在其下运行的注册表项的名称
@@TIMETICKS返回每个时钟周期的微秒数
@@TRANCOUNT返回当前连接的活动事务数
@@VERSION 返回当前安装的日期、版本和处理器类型

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局部变量

注意:定义局部变量必须以@开头。只能在当前连接（会话）下使用

定义变量

--declare @变量名变量类型= 变量值;
--如
declare @name varchar(20)= '任我行';

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局部变量赋值

1. select 赋值
3. declare @age int= 0; -- 定义变量
5. -- 直接赋值
6. select @age = 20;
8. -- 也可通过查询语句进行赋值
9. select @age=Age from person where Name='高圆圆';
10. set 赋值
12. set @age = 20; -- 不可通过查询语句进行赋值
13. declare @username nvarchar(50)='任我行'; --定义局部变量,并赋初始值
14. set @username='张三'; --通过set赋值
15. select @username='aaa'; --通过select 赋值
16. select @username as 用户名; --通过select 输出并取别名
17. print @username; --print 打印输出
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案例
[code]-- 查询高圆的年龄,如果年龄是1-10岁,则输出儿童,10-25 输出少年,25-40输出青年,40-60输出中年,其他老年declare @age int=0;select @age=Age from person where Name='高圆圆';set @age=30; --给局部变量赋值if @age