Need help with the SQL Server Database (How to work with data types)

USE [master] GO CREATE DATABASE [jb] GO USE [jb] GO CREATE TABLE [dbo].[customer]( [customer_number] [int] NOT NULL, [customer_name] [varchar](10) NULL, [customer_company] [varchar](10) NULL, [saleman_employee_number] [decimal](5, 0) NULL, PRIMARY KEY CLUSTERED ( [customer_number] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO /****** Object: Table [dbo].[department] ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO SET ANSI_PADDING ON GO CREATE TABLE [dbo].[department]( [department_number] [decimal](2, 0) NOT NULL, [department_name] [varchar](14) NULL, [location] [varchar](13) NULL ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO /****** Object: Table [dbo].[employee] ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO SET ANSI_PADDING ON GO CREATE TABLE [dbo].[employee]( [employee_number] [decimal](4, 0) NOT NULL, [employee_name] [varchar](10) NULL, [job] [varchar](9) NULL, [manager] [decimal](4, 0) NULL, [hire_date] [datetime] NULL, [salary] [decimal](7, 2) NULL, [commision] [decimal](7, 2) NULL, [department_number] [decimal](2, 0) NULL ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO INSERT [dbo].[customer] ([customer_number], [customer_name], [customer_company], [saleman_employee_number]) VALUES (1, N'Bill', N'Dell', CAST(7499 AS Decimal(5, 0))) GO INSERT [dbo].[customer] ([customer_number], [customer_name], [customer_company], [saleman_employee_number]) VALUES (2, N'Diana', N'Dell', CAST(7499 AS Decimal(5, 0))) GO INSERT [dbo].[customer] ([customer_number], [customer_name], [customer_company], [saleman_employee_number]) VALUES (3, N'Bob', N'HP', CAST(7521 AS Decimal(5, 0))) GO INSERT [dbo].[customer] ([customer_number], [customer_name], [customer_company], [saleman_employee_number]) VALUES (4, N'Jill', N'Asus', CAST(7654 AS Decimal(5, 0))) GO INSERT [dbo].[customer] ([customer_number], [customer_name], [customer_company], [saleman_employee_number]) VALUES (5, N'Jack', N'Best Buy', NULL) GO INSERT [dbo].[customer] ([customer_number], [customer_name], [customer_company], [saleman_employee_number]) VALUES (6, N'Erin', N'Walmart', NULL) GO INSERT [dbo].[department] ([department_number], [department_name], [location]) VALUES (CAST(10 AS Decimal(2, 0)), N'ACCOUNTING', N'NEW YORK') GO INSERT [dbo].[department] ([department_number], [department_name], [location]) VALUES (CAST(20 AS Decimal(2, 0)), N'RESEARCH', N'DALLAS') GO INSERT [dbo].[department] ([department_number], [department_name], [location]) VALUES (CAST(30 AS Decimal(2, 0)), N'SALES', N'CHICAGO') GO INSERT [dbo].[department] ([department_number], [department_name], [location]) VALUES (CAST(40 AS Decimal(2, 0)), N'OPERATIONS', N'BOSTON') GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7369 AS Decimal(4, 0)), N'SMITH', N'CLERK', CAST(7902 AS Decimal(4, 0)), CAST(0x000095C000000000 AS DateTime), CAST(800.00 AS Decimal(7, 2)), NULL, CAST(20 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7499 AS Decimal(4, 0)), N'ALLEN', N'SALESMAN', CAST(7698 AS Decimal(4, 0)), CAST(0x0000960100000000 AS DateTime), CAST(1600.00 AS Decimal(7, 2)), CAST(300.00 AS Decimal(7, 2)), CAST(30 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7521 AS Decimal(4, 0)), N'WARD', N'SALESMAN', CAST(7698 AS Decimal(4, 0)), CAST(0x0000960300000000 AS DateTime), CAST(1250.00 AS Decimal(7, 2)), CAST(500.00 AS Decimal(7, 2)), CAST(30 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7566 AS Decimal(4, 0)), N'JONES', N'MANAGER', CAST(7839 AS Decimal(4, 0)), CAST(0x0000962A00000000 AS DateTime), CAST(2975.00 AS Decimal(7, 2)), NULL, CAST(20 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7654 AS Decimal(4, 0)), N'MARTIN', N'SALESMAN', CAST(7698 AS Decimal(4, 0)), CAST(0x000096DD00000000 AS DateTime), CAST(1250.00 AS Decimal(7, 2)), CAST(1400.00 AS Decimal(7, 2)), CAST(30 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7698 AS Decimal(4, 0)), N'BLAKE', N'MANAGER', CAST(7839 AS Decimal(4, 0)), CAST(0x0000964700000000 AS DateTime), CAST(2850.00 AS Decimal(7, 2)), NULL, CAST(30 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7782 AS Decimal(4, 0)), N'CLARK', N'MANAGER', CAST(7839 AS Decimal(4, 0)), CAST(0x0000966E00000000 AS DateTime), CAST(2450.00 AS Decimal(7, 2)), NULL, CAST(10 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7788 AS Decimal(4, 0)), N'SCOTT', N'ANALYST', CAST(7566 AS Decimal(4, 0)), CAST(0x00009ECA00000000 AS DateTime), CAST(3000.00 AS Decimal(7, 2)), NULL, CAST(20 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7839 AS Decimal(4, 0)), N'KING', N'PRESIDENT', NULL, CAST(0x0000970F00000000 AS DateTime), CAST(5000.00 AS Decimal(7, 2)), NULL, CAST(10 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7844 AS Decimal(4, 0)), N'TURNER', N'SALESMAN', CAST(7698 AS Decimal(4, 0)), CAST(0x000096C900000000 AS DateTime), CAST(1500.00 AS Decimal(7, 2)), CAST(0.00 AS Decimal(7, 2)), CAST(30 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7876 AS Decimal(4, 0)), N'ADAMS', N'CLERK', CAST(7788 AS Decimal(4, 0)), CAST(0x00009EEC00000000 AS DateTime), CAST(1100.00 AS Decimal(7, 2)), NULL, CAST(20 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7900 AS Decimal(4, 0)), N'JAMES', N'CLERK', CAST(7698 AS Decimal(4, 0)), CAST(0x0000971F00000000 AS DateTime), CAST(950.00 AS Decimal(7, 2)), NULL, CAST(30 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7902 AS Decimal(4, 0)), N'FORD', N'ANALYST', CAST(7566 AS Decimal(4, 0)), CAST(0x0000971F00000000 AS DateTime), CAST(3000.00 AS Decimal(7, 2)), NULL, CAST(20 AS Decimal(2, 0))) GO INSERT [dbo].[employee] ([employee_number], [employee_name], [job], [manager], [hire_date], [salary], [commision], [department_number]) VALUES (CAST(7934 AS Decimal(4, 0)), N'MILLER', N'CLERK', CAST(7782 AS Decimal(4, 0)), CAST(0x0000975200000000 AS DateTime), CAST(1300.00 AS Decimal(7, 2)), NULL, CAST(10 AS Decimal(2, 0))) GO