數(shù)據(jù)庫查詢語句

1、數(shù)據(jù)庫操作歸納SqlServer數(shù)據(jù)庫操作語句(步驟)：1. 新建數(shù)據(jù)庫：create database 數(shù)據(jù)庫名稱 ; 例：create database LianXi;use 數(shù)據(jù)庫名稱 ; 例：use LianXi;2. 新建表：create table 表名稱(屬性名/字段名 屬性/字段類型 identity(1,1) primary key not null,屬性名/字段名 屬性/字段類型 not null,屬性名/字段名 屬性/字段類型);例：create table yonghu(uid int identity(1,1) primary key not null,uname c

2、har(10) not null,upass char(10) not null,gender char(2),shouru int,birthday datetime,note text );3. 查詢數(shù)據(jù) ： 基本查詢：-簡單查詢- select * from 表名稱； 例：select * from yonghu; SELECT DISTINCT 表中字段名 AS 字段名別名, YEAR(GETDATE()-YEAR(字段名如生日) AS 如年齡FROM 表名例：select distinct uname as 姓名 , year(getdate()-year(birthday) as

3、年齡 from yonghu; 如下圖所示： SELECT COUNT(*) AS 總數(shù) FROM 表名 -獲取表中行的總數(shù)例：select count(*) as 總數(shù) from yonghu;SELECT AVG(字段名) AS 平均值 FROM 表名 -獲取平均值例：select avg(shouru) as 平均收入 from yonghu;-帶條件查詢-條件表達(dá)式：可以是單表的條件表達(dá)式，又可以是多表之間的條件表達(dá)式。比較符：=（等于）、!=（不等于）、>(大于)、<(小于)、>=(大于等于)、<=(小于等于)、<>(不等于) 例：在用戶表中，列出

4、收入在2000元以上的員工記錄SELECT * FROM yonghu WHERE shouru > 2000; 例：在用戶表中，查出男用戶的平均收入SELECT AVG(shouru) AS 平均收入 FROM yonghu WHERE gender=男; 例：某表如employee表，查詢出市場部和銷售部的員工名單SELECT d.employee_name, e.employee_name FROM employee.e INNER JOIN department d ON e.department_id = d.department_id WHERE d.department_n

5、ame IN (市場部,銷售部)-或-SELECT d.employee_name, e.employee_name FROM employee.e INNER JOIN department d ON e.department_id = d.department_id WHERE (d.department_name = 市場部) OR (d.department_name = 銷售部 ) 對(duì)yonghu表，查出月工資在2000-3000元之間的員工名單SELECT * FROM yonghu WHERE shouru BETWEEN 2000 AND 3000-或-SELECT * FRO

6、M yonghu WHERE shouru >= 2000 AND shouru <= 3000 對(duì)yonghu 表，查出所有姓“張”的員工名單SELECT * FROM yonghu WHERE uname LIKE 張%-或-SELECT * FROM yonghu WHERE LEFT(uname,1) = 張 -查詢結(jié)果處理- 排序輸出（ORDER BY） -ASC：(默認(rèn)) 按升序排列；DESC：按降序排列SELECT uid,uname,upass, shouru FROM yonghu ORDER BY gender , shouru DESC 重定向輸出（INTO）

7、INTO子句用于把查詢結(jié)果放到一個(gè)新建的表中例：某表如，對(duì)部門表department和員工表employee，查詢出市場部所有員工的信息，并將結(jié)果存入newtable中。SELECT employee.* INTO newtable FROM employee INNER JOIN department ON employee .department_id = department.department_id WHERE department.department_name = 市場部 輸出合并（UNION）合并查詢就是使用UNION操作符將來自不同查詢的數(shù)據(jù)組合起來，形成一個(gè)具有綜合信息的查

8、詢結(jié)果，UNION操作會(huì)自動(dòng)將重復(fù)的數(shù)據(jù)剔除。必須注意的是，參加合并查詢的各子查詢使用的表結(jié)構(gòu)應(yīng)該相同，即各子查詢中的數(shù)據(jù)數(shù)目和對(duì)應(yīng)的數(shù)據(jù)類型都必須相同。 例：對(duì)某表：如employee表，列出部門編號(hào)為D001或D002的所有員工姓名SELECT employee_name,department_id FROM employee WHERE department_id = D001UNION SELECT employee_name,department_id FROM employee WHERE department_id = D002 如下圖示 分組統(tǒng)計(jì)（GROUP BY）與篩選（HA

9、VING）例：對(duì)某表，如對(duì)employee表，分別統(tǒng)計(jì)男女員工人數(shù)SELECT sex,COUNT(sex) as 人數(shù) FROM employee GROUP BY sex 如下圖所示例：某表，如對(duì)employee表，分別統(tǒng)計(jì)個(gè)部門男女員工的人數(shù)SELECT department_id,sex,COUNT(*) AS 人數(shù) FROM employee GROUP BY department_id,sex 如下圖所示例：某表，如對(duì)employee表，查出部門平均工資大于2000元的部門編號(hào)SELECT department_id,AVG(wages) AS 平均工資FROM employee

10、GROUP BY department_id HAVING AVG(wages)>=2000 使用COMPUTE和COMPUTE BY子句匯總：使用COMPUTE子句可以在查詢的結(jié)果集中產(chǎn)生成匯總行的同時(shí)，還生成明細(xì)行，可以計(jì)算子組的匯總值。使用COMPUTE BY子句可以對(duì)結(jié)果集數(shù)據(jù)進(jìn)行分組統(tǒng)計(jì)，即計(jì)算分組的匯總值。例：某表，如對(duì)employee表中部門編號(hào)臥位D001的員工工資，按照其部門編號(hào)生成匯總行和明細(xì)行SELECT department _id ,wages FROM employee WHERE department_id = D001ORDER BY department

11、_id COMPUTE sum(wages) 如下圖所示例：某表，如對(duì)employee表中的部門編號(hào)為D001或D002的員工工資，按照其部門編號(hào)生成分組匯總行和明細(xì)行SELECT department_id,wages FROM employee WHERE department_id = D001OR department_id = D002 ORDER BY department_id COMPUTE sum(wages) BY department_id 如下圖所示 嵌套查詢：（由里向外處理。子查詢的SELECT語句中不能使用ORDER BY子句，ORDER BY子句只能對(duì)最終查詢結(jié)果

12、排序） 單值嵌套查詢-子查詢的返回結(jié)果是一個(gè)值的嵌套查詢例：某表，如對(duì)Sales數(shù)據(jù)庫，查詢出市場部的所有員工的編號(hào)SELECT employee_id FROM employee WHERE department_id = (SELECT department_id FROM department WHERE department_name=市場部) 多值嵌套查詢-子查詢的返回結(jié)果是一列值的嵌套查詢 a. ANY運(yùn)算符用法：例：某表，如對(duì)Sales數(shù)據(jù)庫，列出D001號(hào)部門中工資比D002號(hào)部門的員工最低工資高的員工和工資SELECT employee_id,wages FROM emplo

13、yee WHERE department_id = D001AND wages>ANY (SELECT wages FROM employee WHERE department_id = D002)b. All運(yùn)算符的用法：例：某表，如對(duì)Sales數(shù)據(jù)庫，查詢出部門編號(hào)為D001的員工，這些員工的工資比部門為D002的員工的最高工資還要高的員工的編號(hào)和工資。SELECT employee_id,wages FROM employee WHERE department_id =D001AND wages>All（SELECT wages FROM employee WHERE dep

14、artment_id =D002） c. IN運(yùn)算符的用法：例：某表，如對(duì)Sales數(shù)據(jù)庫，列出部門為市場部或銷售部的所有員工的編號(hào)SELECT employee_id FROM employee WHERE department_id IN (SELECT department_id FROM department WHERE department_name = 市場部 OR department_name=銷售部) 連接查詢：（通過連接運(yùn)算符可以實(shí)現(xiàn)多個(gè)表查詢。連接是關(guān)系數(shù)據(jù)庫模型的主要特點(diǎn)，也是它區(qū)別于其它類型數(shù)據(jù)庫管理系統(tǒng)的一個(gè)標(biāo)志。）例：某表，如對(duì)Sales數(shù)據(jù)庫輸出所有員工的銷售單

15、，要求給出員工編號(hào)、姓名、商品編號(hào)、商品名和銷售數(shù)量。SELECTemployee.employee_id,employee.employee_name,goods.goods_id,goods.goods_name,sell_order.order_num FROM employee,sell_order,goods WHERE employee.employee_id = sell_order.employee_id and sell_order.goods_id = goods.goods_id 如下圖所示 內(nèi)連接a. 等值連接：在連接條件中使用等號(hào)（=）運(yùn)算符比較被連接列的列值，按對(duì)應(yīng)

16、列的共同值將一個(gè)表中的記錄與另一個(gè)表中的記錄相連接，包括其中的重復(fù)列。例：某表，如Sales數(shù)據(jù)庫中部門表department和員工表employee的等值連接。SELECT * FROM department INNER JOIN employee ON employee.department_id = department.department_idb. 不等值連接：在連接條件中用除等于（=）運(yùn)算符以外的其他比較運(yùn)算符比較被鏈接的列的列值。這些運(yùn)算符包括>、>=、<=、<、!>、!<和<>。例：某表，如Sales數(shù)據(jù)庫，列出銷售G00001產(chǎn)

17、品的員工中，銷售數(shù)量大于編號(hào)為E001的員工銷售該類產(chǎn)品銷售數(shù)量的那些員工的編號(hào)和銷售數(shù)量。SELECT a.employee_id,a.order_num FROMsell_order a INNER JOIN sell_order b ON a.order_num> b.order_num AND a.goods_id = b.goods_id WHERE(b.goods_id = G00001)AND (b.employee_id = E001)c. 自然連接：在連接條件中使用等于（=）運(yùn)算符比較被連接列的列值，它使用選擇列表方式來指出查詢結(jié)果集合中所包括的列，并刪除連接表中的重復(fù)

18、列。例：某表，如Sales數(shù)據(jù)庫中部門表department和員工表employee的自然連接。SELECT a.department_name,b.*FROM department a INNER JOIN employee b ON b.department_id = a.department_id 外連接：在內(nèi)連接查詢時(shí)，返回查詢結(jié)果集合中的僅是符合查詢條件（WHERE搜索條件或HAVING條件）和連接條件的行。而采用外連接時(shí)，它返回到查詢結(jié)果集合中的不僅包含符合連接條件的行，而且還包括左表（左外連接時(shí)）、右表（右外連接時(shí)）或兩個(gè)連接表（全外連接）中的所有數(shù)據(jù)行。a. 使用作外連接：左外

19、連接通過左向外連接引用左表的所有行。例：某表，如員工表employee做外連接銷售表sell_order.SELECTa.employee_id,a.employee_name,b.goods_id,b.order_num,b.send_date FROM employee a LEFT OUTER JOIN sell_order b ON a.employee_id = b.employee_id 如圖所示b. 使用右外連接：右外連接通過右向外連接引用右表的所有行例：某表，如員工表employee右外連接銷售表sell_order。為了說明方便，先在sell_order表中插入一條銷售信息。

20、INSERT INTO sell_order(order_id1,goods_id,employee_id,customer_id,transporter_id,order_num,discount,order_date,send_date,arrival_date,cost)VALUES(S0006,G0005,C0006,T0002,21,0.5,GETDATE(),GETDATE(),100)SELECT a.employee_id,a.employee_name,b.goods_id,b.order_num,b.send_date,b.order_id1 FROM employee a

21、 RIGHT OUTER JOIN sell_order b ON a.employee_id = b.employee_idb. 使用全外連接全外連接返回兩個(gè)表的所有行。不管兩個(gè)表的行是否滿足連接條件，均返回查詢結(jié)果集。對(duì)不滿足連接條件的記錄，另一個(gè)表相對(duì)應(yīng)字段用NULL代替。SELECT a.employee_id,a.employee_name,b.goods_id,b.order_num,b.send_date,b.order_id1 FROM employee a FULL OUTER JOIN sell_order b ON a.employee_id = b.employee_i

22、d 如下圖所示 交叉連接：交叉連接不帶WHERE子句，它返回被連接的兩個(gè)表所有數(shù)據(jù)行的笛卡爾積，返回到結(jié)果集合中的數(shù)據(jù)行數(shù)等于第一個(gè)表中符合查詢條件的數(shù)據(jù)行數(shù)乘以第二個(gè)表中符合查詢條件的數(shù)據(jù)行數(shù)。例：SELECT a.department_id,a.department_name,b.employee_id,b.employee_name FROM department a CROSS JOIN employee b 如下圖所示 4插入數(shù)據(jù)INSERT INTO 表名 (屬性1,屬性2,屬性3,) VALUES (屬性值1,屬性值2,屬性值3,) 。注：into 可省略。例：INSERT IN

23、TO yonghu (uname,upass) VALUES ('土豆','321');5. 刪除數(shù)據(jù)DELETE FROM 表名 WHERE 條件例：DELETE FROM yonghu WHERE uid=1;例：在DELETE中使用聯(lián)接或子查詢某表操作，如下：-基于Transact-SQL,使用表的聯(lián)接DELETE Sell_Order FROM Sell_Order SO INNER JOIN customer2 C ON SO.customer_id = C.customer_id WHERE C.address LIKE 東方市% 注：SO，C均為別名-等同于下列命令DELETE Sell_Order FROM Sell_Order SO,customer2 C WHERE SO.customer_id = C.customer_id AND C.address LIKE 東方市%-基于SQL-92標(biāo)準(zhǔn)，須使用子查詢DELETE FROM Sell_Order WHERE customer_id IN (SELECT customer_id FROM customer2 WHERE address LIKE 東方市%)6. 更新數(shù)據(jù)UPDATE 表名 SET 屬性名=屬性值,屬性名=屬