Скачать с ютуб SQL Constraints (Not Null, Unique, Check, Default, Primary and Foreign Key). Session 18 в хорошем качестве

SQL Constraints (Not Null, Unique, Check, Default, Primary and Foreign Key). Session 18

SQL constraints Constraints in SQL Server are predefined rules that you can enforce on single or multiple columns We will explore the following constraints in SQL Server in this article. • NOT NULL • UNIQUE • CHECK • DEFAULT • PRIMARY KEY • FOREIGN KEY ---------------------------------------------------------------------------- select * from empdetails truncate table empdetails delete from empdetails where id=4 insert into empdetails values(1,'sunny','A', 1000,'Noida') insert into empdetails values(2,'yogesh','B', 2000,'Delhi') insert into empdetails values(3,'Nisha','C', 3000,'Himachal') ------------------------------------------------------------------------------------------------------ alter table empdetails alter column salary int not null alter table empdetails add constraint unqconstraint unique(name) alter table empdetails add constraint chkconstraint check(salary greater than 2000) alter table empdetails add constraint defconstraint default 'NA' for name alter table empdetails add constraint prmconstraint primary key(id) alter table empdetails drop constraint prmconstraint ---------------------------------------------------------------------------------------------------------- create table emp ( id int, name varchar(20), father varchar(20) ) insert into emp values(1,'suresh', 'bhushan') insert into emp values(2,'mahesh', 'ramesh') insert into emp values(3,'raju', 'vignesh') create table salary ( id int, name varchar(20) ) insert into salary values(1, 1000) insert into salary values(2, 2000) insert into salary values(3, 3000) select * from emp select * from salary exec sp_rename 'salary.name', 'salary', 'column' delete from emp where id=3 delete from salary where id=3 alter table emp add constraint prmyconstraint primary key(id) alter table salary add constraint forgnconstraint foreign key(id) references emp(id)