1 --查询 2 select DB_ID(‘B2C‘) 3 4 --检查数据库是否存在 5 if DB_ID(‘B2C‘) is not null 6 7 --使用数据库 8 use B2C 9 10 --单引号表示字符串，双引号则不是 U 表示用户表 11 select OBJECT_ID(‘UserName‘,‘U‘) 12 --主键约束Primary key 13 --唯一约束Unique 14 --外键约束foreign key () references 15 --检查约束Check 16 --非空约束 17 18 --Select 语句的元素 19 --From 20 --Where 21 --Group by 22 --Having 23 --Select 24 --Order by 25 26 --表达式 27 select orderdate,year(orderdate) as 订单年份 28 from Orders; 29 --选择 30 select orderdate,year(orderdate) as 订单年份 31 from Orders 32 where year(orderdate)=2006 33 34 --查询同一年出生的员工人数 35 select YEAR(birthdate),COUNT(*) 36 from Employee 37 group by YEAR(birthdate) 38 39 --百分比 40 select top (20) percent lastname,firstname 41 from hr.employees 42 43 --开窗函数 over 44 select lastname,firstname,count(*) over () 45 from hr.employees 46 47 --带有总价的订单 48 --partition by 相当于做一个相对的选择，选出等于的值 49 select lastname,firstname,val 50 ,sum(val) over( partition by custid) as 顾客总价 51 ,sum(val) over() as 总价 52 from Sales.OrderValues 53 54 --排名函数 55 --row_number 行号 必须与 over 配合 56 --rank 排名 57 --dense_rank 密集排名 58 --ntile 分组 59 select row_number() over( order by lastname ),lastname,firstname 60 rank() over( order by country) as 排名, 61 dense_rank() over( order by country) as 密集排名, 62 ntile(5) over( order by country) as 分组, 63 from hr.employees 64 65 66 --排名结合部分 67 select row_number() over( order by country) 68 row_number() over( partition by country order by country), 69 country,lastname,firstname 70 from hr.employees 71 72 --between and 73 select * 74 from OrderValues 75 where val between 1000 and 200 76 77 --in 枚举值 78 select * 79 from OrderValues 80 where custid in (1,2,8) 81 82 83 --like 字符串匹配 % 任意多个任意字符 _任意一个任意字符 84 85 86 87 --简单表达式 88 select lastname,region, 89 case region -switch 90 when ‘WA‘ then ‘华盛顿‘ --case 91 else ‘其他特区‘ 92 end 93 from employees 94 95 --搜索表达式 96 select lastname,region, 97 case 98 when region=‘WA‘ then ‘华盛顿特区‘ 99 when region is null then ‘位置地区‘ 100 else ‘其它地区‘ 101 end 102 from employees; 103 104 105 --定义变量 106 declare @s char(10), 107 --赋值之后,实际上已经填满了10个字符 108 set @s=‘hello‘ 109 print @s 110 set @s = @s+‘world‘ 111 print @s 112 113 --注意：在SQL 中，下标从1开始 114 select productname,substring(productname,9,10) 115 from production.Products 116 117 --left 表示左边 118 select productname, left(productname,8) 119 from production.Products 120 121 --right 表示取右边的部分 122 select productname,right(productname,8) 123 from production.Products 124 125 --模版在前，源字符串在后，空格出现在名字中的位置，从1开始 126 select productname,charindex(‘‘,productname) 127 from production.Products 128 129 --将产品名称中的product 替换为产品名 130 select productname,replace(productname,‘Product‘,‘产品名‘) 131 from production.Products 132 133 --stuff 替换 134 select productname,stuff(productname,8,1,‘ : ‘) 135 from production.Products 136 137 --转换大写 和 小写 138 select productname,upper(productname),lower(productname) 139 from production.Products 140 141 --去空格 142 select datalength(rtrim(string)) 143 select ltrim(rtrim(string)) 144 145 146 --字符串方式表示日期 147 select orderid,orderdate 148 from Sales.orders 149 where orderdate > ‘20080301‘ 150 151 --cast 转换 datetime 这个和上面一个是等价的 152 select orderid,orderdate 153 from Sales.orders 154 where orderdate > cast (‘20080301‘ as datetime) 155 156 -- datepart 取日期中的一部分 157 select getdate() 158 159 --年，月，日，小时，分钟，秒 160 select datepart(year,getdate()), 161 datepart(month,getdate()), 162 datepart(day,getdate()), 163 datepart(hour,getdate()), 164 datepart(minute,getdate()), 165 datepart(second,getdate() 166 167 --特殊 168 select datepart(dayofyear,getdate()),-- 从年初到现在的天数 169 datepart(weekday,getdate()),--星期几，从星期天开始为1 170 datepart(week,getdate()) --今年的第几周 171 172 select year(getdate()),month(getdate()),day(getdate() 173 174 --日期加和减 日期加法 单位 175 select getdate(),dateadd(month,2,getdate()) -- 加两个月 176 dateadd(year,3,getdate()), 177 dateadd(minute,30,getdate()) 178 179 --日期减法 单位 180 select datediff(year,‘19491001‘,getdate()) 181 182 --计算今年多少岁 183 select datediff(year,‘19800101‘,getdate()) 184 185 --练习1 186 select * 187 from Sales.Orders 188 where year(orderdate)=2007 and month(orderdate)=7 189 190 select * 191 from Sales.Orders 192 where datepart(year,orderdate)=2007 and 193 datepart(month,orderdate)=6 194 --还可以 ‘200706‘ 195 --将日期转换成字符串 196 select * 197 from Sales.Orders 198 where left(convert(nvarchar,(orderdate),112),6)=‘200706‘ 199 200 select getdate(),convert(nvarchar,getdate(),112), 201 left(convert(nvarchar,getdate(),112),6) 202 203 select convert(int,‘99‘)+100 204 select cast(‘99‘ as int)+100 205 206 select orderid,sum(unitprice * qty) 207 from Sales.Orderdatails 208 group by orderid 209 having sum(unitprice *qty) >10000 210 order by sum(unitprice * qty) desc 211 212 --3-1交叉连接和内连接 213 --连接查询 cross 翻译十字 所以的都做了一次匹配 214 select empid,shipperid 215 from Hr.employees cross join Sales.Shippers 216 217 --内连接 必须符合特定条件的组合 218 select c.categoryid,productid,p.productname,c.categoryname 219 from production.Categories c inner join production.products p 220 on c.categoryid=p.categoryid 221 222 --查询每个顾客的名称，已经下过多少张订单 223 select distinct c.custid,contactname,orderid, 224 count(*) over(partition by o.custid) 225 from Sales.Customers c inner join Sales.Orders o 226 on c.custid=o.custid 227 228 --插入10 条记录 229 insert into digits (digit) 230 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); 231 232 --生成数字 233 select d1.digit,d2.digit, d3.digit* 10 + d2.digit*10 +d1.digit 234 from digits di cross join digits d2 235 cross join digits d3 236 237 --实现1-1000 238 select row_number() over(order by d1.digit) as digit 239 from digits d1 cross join digits d2 240 cross join digits d3 241 order by digit 242 243 --查询每张订单多少钱 244 select distinct o.orderid,orderdate, 245 sum(qty * unitprice) over(partition by o.orderid) 246 from Sales.Orders o inner join Sales.OrderDatails d 247 on o.orderid=d.orderid 248 249 --左外连接 250 select count(*) 251 from Sales.Customers c left outer join Sales.Order o 252 on c.sutid =o.custid 253 254 --右外连接 255 select count(*) 256 from Sales.Customers c right outer join Sales.Order o 257 on c.sutid =o.custid 258 259 --组函数不包含 Null 260 select distinct c.contactname, 261 count(o.orderid) over(partition by c.custid) ordercount 262 from Sales.Customers c left outer join Sales.Orders o 263 on c.custid=o.custid 264 order by ordercount 265 266 --查询一下所有的雇员都处理过订单 267 select e.empid,count(o.orderid),lastname 268 from hr.employee e left outer join sales.orders o 269 on e.empid=o.empid 270 group by e.empid,lastname 271 having count(o.orderid)=0 272 273 274 --将员工表和订单表做一个外连接 275 select e.empid,e.lastname 276 from left outer join sales.orders o 277 where o.orderis is null 278 279 --查询有顾客但是没有供应商的国家 280 select distinct c.country as 客户国家,s.country as 供应商国家 281 from Sales.Customers c left outer join Production.Suppliers s 282 on c.country=s.country 283 where c.country is null 284 285 --全外连接，查询所有的国家，有无供应商，有无顾客 286 select distinct c.country as 客户国家,s.country as 供应商国家 287 from Sales.Customers c full outer join Production.Suppliers s 288 on c.country=s.country 289 290 --2008年中 ，每天有多少订单 291 select orderdate,count(*) 292 from sales.orders 293 where orderdate between ‘20080101‘ and ‘20081231‘ 294 group by orderdate 295 296 select orderdate,count(*) over (partition order by orderdate) 297 from sales.orders 298 where orderdate between ‘20080101‘ and ‘20081231‘ 299 300 --创建一个表，向表里写入400条数据 301 create table nums 302 ( 303 n int 304 ) 305 declare @i int 306 set @i=1 307 while @i<400 308 begin 309 set @i=@i+1 310 insert into values(@i) 311 end 312 313 --制作一个连续的日期 314 315 select dateadd(day,n,‘20071231‘) 316 from nums 317 318 --与订单表做一个连接 319 select dateadd(day,nums.n,‘20071231‘) noorderdate 320 from nums left outer join salas.orders 321 on dateadd(day,nums.n,‘20071231‘)=sales.orders.orderdate 322 where sales.orders.orderid is null 323 order by noorderdate 324 325 326 --子查询 327 select lastname 328 where birthdate=(select max(birthdate) from hr.employees) 329 330 --独立子查询 没有用到外部的子查询叫独立子查询 331 332 333 --相关子查询 解释: 子查询查询出现了子查询以外的查询叫做相关子查询 334 select custid,contactname, 335 ( 336 select count(*) 337 from Sales.Orders 338 where Sales.Orders.custid=Sales.Customerscustid 339 ) as ordercount 340 from Sales.Customers 341 342 --还有一些复杂的情况考虑 343 --多值子查询 这里用 exists 也可 是否存在 344 select distinct country 345 from Sales.Customers 346 where country not in 347 ( 348 select distinct country 349 from Production.Suppliers 350 ) 351 --使用相关子查询 352 select distinct country 353 from Sales.Customers c 354 where 355 not exists 356 ( 357 select country from Production.Suppliers s 358 where s.country=c.country 359 ) 360 361 362 --高级子查询 363 364 --查询一个数字的上一个数和下个数 使用相关子查询 365 select orderid, 366 ( 367 select max(orderid) 368 from Sales.orders innerT 369 where innerT.orderid < outerT.orderid 370 ) as prevOrder, 371 ( 372 select min(orderid) 373 from Sales.orders innerT 374 where innerT.orderid> outerT.orderid 375 ) as nextOrder 376 from Sales.Order outerT 377 378 379 select e.empid,fistname,lastname 380 from Sales.Orders o right outer join Hr.Employees e 381 on o.empid=e.empid and o.orderdate>=‘20080501‘ 382 where o.orderid is null 383 384 --客户表中出现过,雇员表中没有出现过的国家 385 select distinct country 386 from Sales.Customers 387 where country not in ( 388 select country 389 from hr.employees 390 ) 391 --考虑用连接 392 select c.country 393 from Sales.Cutomers c left outer join Hr.Employees e 394 on c.country =e.country 395 where c.country is null 396 397 398 399 --派生表 其实就是特殊的子查询 400 --用在from 之后的子查询 401 --特殊之处 402 -- 1.必须起别名,派生表必须起别名, 表达式必须起别名 403 select * 404 from ( 405 select custid,count(*) over(partition by country) as num 406 from Sales.Customers 407 where country=‘USA‘ 408 ) t 409 --或者在外面起别名 t 的后面(custid,num) 410 411 --表表达式 412 --公用表表达式CTE 跟派生表很相似 413 414 --派生表实现 415 select * 416 from 417 ( 418 select companyname,country 419 from Sales.Customers 420 where country =‘USA‘ 421 ) t 422 423 --使用CTE 424 --先定义子查询,命名 425 with usa_customers 426 as 427 ( 428 select companyname,country 429 from Sales.Customers 430 where country=‘USA‘ 431 ) 432 select * from usa_customers 433 434 with usa_customers 435 as 436 ( 437 select companyname as 公司名,country 国家 438 from Sales.Customers 439 where country=‘USA‘ 440 ) 441 select * from usa_customers 442 443 --在CTE 使用参数 444 declare @country nvarchar(30); 445 set @country=‘USA‘; 446 with usa_customers(公司名,国家) 447 as 448 ( 449 select companyname,country 450 from Sales.Customers 451 where country=@country 452 ) 453 select * from usa_customers; 454 455 select year(orderdate),custid,count(*) orderdate 456 from Sales.Orders 457 group by year(orderdate),custid 458 having count(*)>10 459 460 select year(orderdate),custid 461 from Sales.Orders 462 463 select orderyear,custid,count(*) 464 from 465 ( 466 select year(orderdate) orderyear,custid 467 from Sales.Orders 468 ) as t1 469 group by orderyear,custid 470 471 select orderyear,custid,orderdate 472 from 473 ( 474 select orderyear,custid,count(*) as ordercount 475 from 476 ( 477 select year(orderdate) orderyear,custid 478 from Sales.Orders 479 ) as t1 480 group by orderyear,custid 481 ) as t2 482 where ordercount>10 483 484 485 --使用CTE 486 with withyearorders (orderyear,custid) 487 as 488 ( 489 select year(orderdate),custid 490 from Sales.Orders 491 ), 492 yearorders 493 as 494 ( 495 select orderyear,custid,count(*) as ordercount 496 from withyearorders 497 group by orderyear,custid 498 ), 499 yearOrder10 500 as 501 ( 502 select orderyear,custid,ordercount 503 from yearoders 504 where ordercount>10 505 ) 506 select * from yearOrder10 507 508 --派生表查询 509 select t1.orderyear,t2.orderyear,t1.custcount-t2.custcount 510 from 511 ) 512 select year(orderdate) as orderyear,count(distinct custid) countcount 513 from Sales.Orders 514 group by year(orderdate) 515 ) as t1 516 left outher join 517 ) 518 select year(orderdate) as orderyear,count(distinct custid) countcount 519 from Sales.Orders 520 group by year(orderdate) 521 ) as t2 522 on t1.orderyear=t2.orderyear+1 523 524 --多个CTE 复用 525 with yearcust 526 as 527 ( 528 select year(orderdate) as orderyear,count(distinct custid) countcount 529 from Sales.Orders 530 group by year(orderdate) 531 ) 532 select curr.orderyear,curr.custcount,prev.oderyear,prev.custcount 533 curr.custcount-prev.custcount 534 from yearcust as curr left outer join yearcust prev 535 on curr.orderyear=prev.orderyear+1 536 537 538 --自连接,连接两遍的表其实是同一张表，一定要起别名 539 select e.empid,e.lastname,e.mgrid,e.empid,m.lastname 540 from Hr.Employees e inner join Hr.Employees m 541 on e.mgrid=e.empid 542 543 544 --查询员工的下属 递归 545 with emplist 546 as 547 ( 548 -- 起点 ,仅仅执行一次 549 select empid,lastname,mgrid 550 from Hr.Employees 551 where mgrid=2 552 union all --合并 553 --可能多次执行,直到查询结果为空 554 select e.empid,e.lastname,e.mgrid 555 from Hr.Employees e inner join emplist m 556 on e.mgrid=m.empid 557 ) 558 select * from emplist 559 option (maxrecursion 6); --限制递归次数 560 561 562 --View 视图 563 --把查询保存在数据库中，起名字，视图 564 create view usacustomers 565 as 566 select companyname,country 567 from Sales.Customers 568 where country=‘USA‘ 569 570 go --前面是单独的,后面再执行 571 572 create view myOrderValues 573 as 574 select o.oderid,custid,empid,shipperid,orderdate, 575 sum(d.qty * d.unitprice) as val 576 from Sales.Orders o inner join Sales.OrderDatails d 577 on o.orderid=d.orderid 578 group by o.orderid,custid,empid,shipperid,orderdate 579 580 --删除视图 581 drop view dbo.usacustomers 582 583 create view CustOrders 584 as 585 select o.custid,datediff(month,datediff(month,0,o.orderdate),0) as ordermonth, 586 sum(od.qty) as qty 587 from Sales.Orders as o inner join 588 Sales.OrderDetails as od on od.orderid=o.orderid 589 group by o.custid,datediff(month,datediff(month,0,o.orderdate),0) 590 591 592 select empid,max(orderdate) as maxorderdate 593 from Sales.Orders 594 group by empid 595 596 select o.empid,o.orderdate,o.orderid,o.custid 597 from 598 ( 599 select empid,max(orderdate) as maxorderdate 600 from Sales.Orders 601 group by empid 602 ) t 603 inner join Sales.Order o 604 on o.orderdate=t.maxorderdate and o.empid=t.empid 605 606 607 with empmaxorder 608 as 609 ( 610 select empid,max(orderdate) as maxorderdate 611 from Sales.Orders 612 group by empid 613 ) 614 select o.empid,o.orderdate,o.orderid,o.custid 615 from Sales.Orders o inner join empmaxorder em 616 on o.empid=em.empid and o.oderdate=em.maxorderdate; 617 618 select orderid,orderdate,custid,empid 619 row_number() over( order by orderdate,orderid) as rownumber 620 from Sales.Orders 621 622 with numorders 623 as 624 ( 625 select orderid,orderdate,custid,empid 626 row_number() over(order by orderdate,orderid) as rownum 627 from Sales.Orders 628 ) 629 select orderid,orderdate,custid,empid,rownum 630 from numorders 631 where rownum between 11 and 20 632 633 --递归CTE 634 with mangers 635 as 636 ( 637 --入口点 638 select empid,mgrid,firstname,lastname 639 from Hr.Employees 640 where empid=9 641 union all 642 --递归查询 643 select e.empid,e.mgrid,e.firsname,lastname 644 from mangers m inner join Hr.Employees e 645 on m.mgrid = e.empid 646 ) 647 select empid,mgrid,firsname,lastname 648 from mangers 649 650 go 651 652 create view Sales.VEmpOrders 653 as 654 select empidi,year(orderdate) as orderyear,sum(qty) as qty 655 from Sales.Orders o inner join Sales.orderdateils od 656 on o.orderid=od.orderid 657 group by empid,year(orderdate) 658 659 660 --连续聚合 661 662 select empid,orderyear,qty 663 ( 664 select sum(qty) 665 from Sales.VempOrders innerT 666 where innerT.empid=outerT.empid 667 and innerT.orderyear<=outerT.orderyar 668 ) as runqty 669 from Sales.VempOrders outerT 670 order by empid,orderyear 671 672 673 with vorders 674 as 675 ( 676 select empidi,year(orderdate) as orderyear,sum(qty) as qty 677 from Sales.Orders o inner join Sales.orderdateils od 678 on o.orderid=od.orderid 679 group by empid,year(orderdate) 680 ) 681 select empid,orderyear,qty 682 ( 683 select sum(qty) 684 from vorders innerT 685 where innerT.empid=outerT.empid 686 and innerT.orderyear<=outerT.orderyar 687 ) as runqty 688 from vorders outerT 689 order by empid,orderyear 690 691 go 692 693 --定义一个表函数 694 create function production.topProducts 695 ( 696 @supid int, 697 @num int 698 ) 699 returns table 700 as 701 return 702 select top(@num) * 703 from Production.Products 704 where supplierid=@supid 705 order by unitprice desc 706 707 --调用 表函数 708 select * 709 from production.topProducts(5,2) 710 711 712 713 --交叉连接 714 select s.supperlierid,companyname, 715 productid,productname,unitprice 716 from Production.Suppliers s 717 cross apply production.topProducts(s.supplierid,2) 718 719 720 --透视,逆透视及分组集合 表的转置 721 722 --分组查询 723 select empid ,custid,sum(qty) sumqty 724 from dbo.orders 725 group by empid,custid 726 727 --对雇员进行分组 728 select empid,sum(qty) 729 from dbo.orders 730 group by empid 731 732 --增加顾客的列 1 号顾客 使用相关子查询 733 select empid, 734 ( 735 select sum(qty) 736 from dbo.orders innerT 737 where custid=1 and innerT empid=outerT empid 738 ) as A, 739 ( 740 select sum(qty) 741 from dbo.orders innerT 742 where custid=2 and innerT empid=outerT empid 743 ) as B, 744 ( 745 select sum(qty) 746 from dbo.orders innerT 747 where custid=3 and innerT empid=outerT.empid 748 ) as C 749 from dbo.orders outerT 750 group by empid 751 752 753 select empid, 754 sum(case when custid=1 then qty end) as A, 755 sum(case when custid=2 then qty end) as B, 756 sum(case when custid=3 then qty end) as C, 757 sum(qty) 758 from dbo.orders 759 group by empid 760 761 762 763 使用 pivot 语法实现透视 764 select empid,count(*) 765 count(case when year(orderdate)=2006 then orderdate end) 766 as nums2006, 767 count(case when year(orderdate)=2007 then orderdate end) 768 as nums2007, 769 ( 770 select count(*) 771 from Sales.Orders innerT 772 where innerT.empid=outerT.empid and year(orderdate)=2008 773 ), 774 sum(qty) 775 from sales.orders outerT 776 group by empid 777 778 779 select empid,[1],[2],[3] 780 from ( 781 --仅仅返回透视中用到的列 782 select empid,qty,custid 783 from dbo.orders 784 ) t --分组是隐含的,对表中除掉聚合和条件的列进行聚合 785 pivot( 786 sum(qty) --聚合函数 787 from custid in([1],[2],[3]) --准备做列名 788 ) as p; 789 790 791 select empid,[2006],[2007],[2008] 792 from 793 ( 794 select empid,year(orderdae) orderyear,orderid 795 from Sales.Orders 796 ) as t 797 piovt 798 ( 799 count(orderid) 800 from orderyear in([2006],[2007],[2008]) 801 ) as p 802 order by empid; 803 804 805 ---计算每个客户每年的支出金额 806 select custid, year(orderdate) as orderyear,sum(od.qty *od.unitprice) totalprice 807 from Salas.Orders o inner join Sales.ORderDatails od 808 group by custid,year(orderdate) 809 810 811 select custid,[2006],[2007],[2008] 812 from ( 813 select custid, year(orderdate) as orderyear,sum(od.qty *od.unitprice) totalprice 814 from Salas.Orders o inner join Sales.ORderDatails od 815 group by custid,year(orderdate) 816 ) t 817 pivot( 818 sum(totalprice) 819 for orderyear in([2006],[2007],[2008]) 820 ) p; 821 822 823 if DB_ID(‘school‘) is not null 824 begin 825 use master; 826 drop database school; 827 end 828 829 create database school; 830 831 use school; 832 833 --schema , 默认 dbo 834 create schema student; 835 go 836 837 if object_id(‘student.Students‘,‘U‘) is not null 838 drop table student.Students; 839 --考虑定义一张表 840 create table student.Students 841 ( 842 studid int identity(1,1) not null,-- 非空约束 843 studentname nvarchar(20) not null, 844 classid int, 845 --外键约束 846 constraint fk_classid foreign key(classId) 847 references classs(id), 848 --性别 849 gender nvarchar(1), 850 --检查约束 851 constraint ck_gender check(gender in(‘男‘,‘女‘)), 852 --唯一约束 853 constraint uq_name unique(studentname), 854 --主键约束，主键中能存在一组，但是唯一约束可以由多组 855 constraint pk_id primary key(studid) 856 ); 857 go 858 --插入数据 全部字段都赋值 859 insert into student.Students values(1,‘tom‘); 860 861 862 863 --通常使用指定字段名的方式 864 insert into student.Students(studentname,studid) 865 values(‘alice‘,2) 866 867 --另外一种写法 868 insert student.Students(studid,studentname) 869 select ‘‘,‘‘ union, 870 select ‘‘,‘‘ union, 871 select ‘‘,‘‘ union, 872 select ‘‘,‘‘ union 873 874 875 876 877 878 select * from student.Students; 879 880 881 --事务和并发 882 883 --隐式事务 884 885 --显示事务，明确指出事务的起止边界 886 begin transaction 887 delete from Sales.Shippers where shipperid=4 888 delete from Sales.Shippers where shipperid=5 889 --回滚 890 rollback 891 --提交 892 commit 893 894 --事务必须有四个属性 895 --原子性(Atomicity),一致性(Consistency),隔离性(Isolation) 896 --持久性(Durabillity) 这四个属性的首字母可以缩写成ACID 897 898 899 --设置隔离级别可以读取未提交的数据 900 set transaction isolation level read uncommitted 901 902 903 --其实就是加锁，加上共享锁 904 --普通情况下，查询的时候，系统加上共享锁，查询结束， 905 --锁撤销 906 --我们现在，希望在查询结束之后，共享锁依然存在，保证数据不被修改 907 908 set transaction isolation level repeatable read; 909 910 911 912 913 --可编程对象 914 --定义变量 915 declare @i int 916 set @i=10 917 print @i; 918 919 declare @i varchar(20) 920 set @i=‘Hello,world‘; 921 print @i; 922 923 declare @i nchar(20) --固定长度 924 set @i=‘Hello‘; --已经占用了所有的空间 925 set @i=@2+‘,world‘; 926 print @i; 927 928 --还可以使用select 对变量赋值 929 select @i=99; 930 print @i; 931 932 --当前时间 933 declare @now datetime 934 set @now=getdate(); 935 print @now; 936 937 938 --查询顾客的数量，保存到变量中使用 939 declare @customerCount int; 940 select @customerCount= count(*) --赋值语句 941 from Sales.Customers; 942 print @customerCount; 943 944 --选择结构 945 --条件 946 --取得当前时间的分钟部分 947 declare @mi int; 948 set @mi=datepart(minute,getdate()); 949 if @mi>10 950 begin 951 print ‘下课‘ 952 end 953 else 954 begin 955 print ‘继续学习‘ 956 end 957 958 break 959 960 961 962 --游标 963 964 select companyname 965 from sales.customers 966 967 --简单变量，标量 968 declare @name nvarchar(100) 969 select @name=companyname 970 from sales.customers; 971 print @name; 972 973 --使用游标 是把数据逐条查询出来 974 --1. 声明游标，基于查询 975 declare c cursor 976 for 977 select custid, companyname 978 from sales.customer 979 980 declare @name nvarchar(100); 981 declare @id int; 982 --2.在使用之前，必须打开游标 983 open c; 984 --3. 从游标中读取查询数据，每次可以读取一条记录 985 fetch next from c into @id,@name 986 --4. 注意fetch 并不一定获取实际的数据 987 while @@fetch_status=0 --成功获取了数据 988 begin 989 print @name; 990 -- 燃火，试探获取下一条数据 991 fetch next from c into @id,@name; 992 end 993 --5. 游标使用完毕，一定要关闭 994 close c; 995 --6.释放游标 996 deallocate c; 997 998 999 --局部临时表 名字前面有一个#表示局部临时表 1000 create table #temptable 1001 ( 1002 num int 1003 ) 1004 --使用与表相同 1005 insert into #temptable (num) values(1),(1),(2),(3),(5); 1006 1007 --全局临时表 1008 --使用方式名字前面有两个## 1009 create table ##globaltable 1010 ( 1011 name nvarchar(20) 1012 ) 1013 --表变量 1014 declare @table table 1015 ( 1016 num int 1017 ) 1018 insert into @table (num) values(1),(1),(2),(3),(5) 1019 select * from @table 1020 1021 --静态SQL 1022 1023 --动态SQL 1024 declare @sql nvarchar(200) 1025 set @sql=‘select companyname from seles.customers‘ 1026 print @sql; 1027 --将一个字符串看成一个SQL 语句动态执行 1028 exec(@sql); 1029 1030 1031 --sql 注入攻击 1032 1033 declare @sql nvarchar(200); 1034 set @sql=‘select custid,companyname from seles.customers where 1035 [email protected]‘; 1036 1037 --用户输入查询的编号 1038 declare @input int; 1039 set @input=23; 1040 --原则，用户的输入是邪恶的 1041 --set @input=‘abc‘; 1042 --set @input=‘0 or 1=1‘; 1043 --set @input=‘0; select * from sales.customers‘; 1044 print @sql; 1045 1046 --将一个字符串看成一个SQL 语句动态执行 1047 exec sp_executesql 1048 @stmt=@sql; --表示要执行的SQL语句 1049 @params= N‘@id as int‘; --声明命令中需要的参数 1050 @id=@input; --后面依次提供参数 1051 go 1052 1053 1054 --调整价格写成一段程序，保存到数据库中 1055 --存储过程 1056 create procedure ModifyPrice 1057 ( 1058 @num money 1059 ) 1060 as 1061 update production products 1062 set unitprice=unitprice=@num; 1063 1064 --存储过程保存在数据库中 1065 exec dbo.ModifyPrice @num=10; 1066 1067 --参数问题 1068 --1.传入参数 1069 -- 传统的参数，默认的参数就是传入参数 1070 --2.传出参数 1071 -- out,ref 参数 1072 1073 --查询顾客的数量 1074 --与方法不同，存储过程没有通常意义上的返回类型和返回值 1075 create procedure GetCustomerCount 1076 ( 1077 @count int output --参数有output 传出参数 1078 ) 1079 as 1080 declare @num int; 1081 select @num=count(*) from sales.customers; 1082 print @num; 1083 1084 --使用带有传出参数的存储过程 1085 --必然使用变量来保存传出的结果 1086 declare @mycount int; 1087 --前面是参数定义的传出参数名称 1088 --后面是 我们定义的用来保存传出结果的变量 1089 exec dbo.GetCustomerCount @count=@mycount output; 1090 print @mycount 1091 1092 1093 create procedure createuser 1094 ( 1095 @username nvarchar(100) 1096 ) 1097 as 1098 declare @namelen int; 1099 set @namelen=len(@username) 1100 if @namelen>=5 1101 return 0 1102 else 1103 return 1; 1104 1105 --调用 获取返回结果是否成功 1106 declare @returnValue int; 1107 exec @returnValue=createuser @username=‘23423432‘ 1108 print @returnValue 1109 1110 --创建函数 1111 create function getminute 1112 ( 1113 @datevalue datetime --传入参数 1114 ) 1115 --函数可以直接返回一个值 1116 returns int 1117 as 1118 --函数体 1119 begin 1120 declare @mi int 1121 set @mi=datepart(minute,@datevalue); 1122 return @mi; 1123 end 1124 1125 --调用 1126 select dbo.getminute(getdate()) 1127 1128 --触发器 1129 --创建一个日志表，记录对货运的操作 1130 create table shipper_log 1131 ( 1132 logid int identity(1,1) primary key, 1133 opdate datetime default getdate(), 1134 opuse nvarchar(20), 1135 op nvarchar(20), 1136 shipname nvarchar(50), 1137 shipphone nvarchar(20) 1138 ) 1139 --创建一个审核货运公司的触发器 1140 create trigger tg_ship 1141 --触发器没有参数，由于通过数据库系统调用 1142 on Sales.Shippers after insert,delete,update 1143 as 1144 insert into shipper_log(opuse,op,shipname,shipphone) 1145 select user_name(),‘插入‘,companyname,phone 1146 from inserted; 1147 1148 --标识问题 1149 --获得系统提供的标识值,获取整个系统系统范围内 1150 select @@identity 1151 1152 --应该使用这个，获取当前作用域中最新生成的标识值 1153 select scope_identity(); 1154 1155 1156 select datepart(day,‘20161228‘,‘20140624‘) 1157 1158 --多表查询 1159 with 1160 a as (select ‘60000‘ cw1, 200 cw2, ‘2010-12-31‘ cw3), 1161 b as (select ‘60000‘ CW1, ‘银行‘ CW2), 1162 c as (select ‘银行‘ cw1, 121 cw2, ‘2010-12-31‘ CW3) 1163 select a.cw1 ‘公司‘,a.cw2 ‘财务‘,b.CW2 ‘行业‘,c.cw2 ‘平均值‘ 1164 from a 1165 inner join b on a.cw1=b.CW1 1166 inner join c on b.CW2=c.cw1 1167 where a.cw2>c.cw2 1168 1169 --参照更新格式 1170 update a 1171 set a.字段=b.字段 1172 from a join b on a.xx=b.xx 1173 where 1174 1175 --查询表中重复的数据 1176 select 字段,sun(1) as c 1177 from 表 1178 group by 字段 1179 having sum(1)>1
时间： 2025-01-21 20:37:53