1 create database mydb 2 use mydb 3 go 4 create table account( 5 id varchar(16), 6 name varchar(16), 7 balance float 8 ) 9 go 10 select * from account 11 12 insert into account(id, name, balance) values('620101', 'liyong', 300) 13 insert into account(id, name, balance) values('620106', 'mali', 400) 14 --insert into account(id, name, balance) values('620009', 'chenying', 800) 15 insert into account(id, name, balance) values('646009', 'chenying', 800) 16 --delete from account where id = '620009' 17 go 18 update account set balance = balance - 1000 where id = '620101' 19 update account set balance = balance + 1000 where id = '620106' 20 --消息 547,级别 16,状态 0,第 1 行 21 --UPDATE 语句与 CHECK 约束"CK_Blance"冲突。该冲突发生于数据库"mydb",表"dbo.account", column 'balance'。 22 --语句已终止。 23 24 go 25 --alter table account 26 --alter COlumn balance int 27 go 28 alter table account 29 add constraint CK_Blance check(balance >= 0) 30 go 31 alter table account 32 drop constraint CK_Blance 33 --定一个事务 34 --从liyong扣钱往mali加钱 35 begin transaction 36 update account set balance = balance - 1000 where id = '620101' 37 if((select balance output from account where id = '620101') < 0) 38 begin 39 PRINT('余额不足!'); 40 ROLLBACK; 41 end 42 else 43 begin 44 update account set balance = balance + 1000 where id = '620106' 45 commit; 46 PRINT('转账成功!'); 47 end 48 go 49 sp_help 50 --备份设备 51 sp_addumpdevice 'disk', 'xk_bak' ,'d:xk_bak' 52 --备份数据库 53 backup database mydb 54 to xk_bak 55 --还原数据库 56 restore database mydb from disk = 'd:xk_bak' 57 with replace; --覆盖