SQL Server defines data integrity 6 constraints

1. Create a customer sheet

1 IF object_id('dbo. Employees','U') is  not NULL2   DROP TABLEdbo. Employees;3 4 CREATE TABLEdbo. Employees5 (6EmpidINT          not NULL,7FirstNameVARCHAR( -) not NULL,8LastNameVARCHAR( -) not NULL,9HireDate DATE not NULL,TenMgridINT         NULL, OneSsnVARCHAR( -) not NULL, ASalary Money        not NULL -);

2. PRIMARY KEY constraints

-- Primary Key ALTER TABLE dbo. Employees  ADDCONSTRAINT  pk_employees  PRIMARYKEY (empid);  

A unique index is created for the primary KEY constraint background, forcing the logical uniqueness constraint on the physical mechanism

3. Unique constraints

-- Unique ALTER TABLE dbo. Employees  ADDCONSTRAINT  unq_employees_ssn  UNIQUE(SSN);

4. Foreign KEY constraint create an order table Insert foreign key

IF object_id('dbo. Orders','U') is  not NULL  DROP TABLEdbo. Orders;CREATE TABLEdbo. Orders (OrderIDINT          not NULL, EmpidINT          not NULL, CustIDVARCHAR(Ten) not NULL, Orderts DATETIME2 not NULL, QtyINT          not NULL,  CONSTRAINTpk_ordersPRIMARY KEY(OrderID));

-- Foreign Keys ALTER TABLE dbo. Orders  ADDCONSTRAINT  fk_orders_employees  FOREIGNKEY  (empid)  REFERENCES dbo. Employees (Empid);

5.CHECK constraints

-- Check ALTER TABLE dbo. Employees  ADDCONSTRAINT  chk_employees_salary  CHECK>  0.00);

6. Default Constraints

-- Default ALTER TABLE dbo. Orders  ADDCONSTRAINT  dft_orders_orderts  DEFAULTfor  orderts; -- Cleanup DROP TABLE dbo. Orders, dbo. Employees;

SQL Server defines data integrity 6 constraints