数据库操作实例

Posted 2020-08-13 orezero

数据库操作实例

 1 DROP TABLE msp;
 2 DROP TABLE party;
 3 
 4 CREATE TABLE party (partyCode VARCHAR(10) NOT NULL
 5                     ,partyName VARCHAR(50)
 6             ,leader VARCHAR(50)
 7             ,PRIMARY KEY (partyCode)
 8             )DEFAULT CHARSET=utf8;
 9     
10 CREATE TABLE msp (mspName VARCHAR(50) NOT NULL
11                   ,party VARCHAR(10)
12           ,constituency VARCHAR(50)
13                   ,PRIMARY KEY (mspName)
14                   ,FOREIGN KEY (party) REFERENCES party(partyCode)
15                   )DEFAULT CHARSET=utf8;
16 
17 CREATE INDEX msp_party ON msp(party);
18 
19 INSERT INTO party VALUES (‘Com‘,‘Communist‘,NULL);
20 INSERT INTO party VALUES (‘Con‘,‘Conservative‘,‘McLetchie MSP, David‘);
21 INSERT INTO party VALUES (‘Green‘,‘Green‘,NULL);
22 INSERT INTO party VALUES (‘Lab‘,‘Labour‘,‘Dewar MSP, Rt Hon Donald‘);
23 INSERT INTO party VALUES (‘LD‘,‘Liberal Democrat‘,‘Wallace QC MSP, Mr Jim‘);
24 INSERT INTO party VALUES (‘NLP‘,‘Natural Law Party‘,NULL);
25 INSERT INTO party VALUES (‘SNP‘,‘Scottish National Party‘,‘Salmond MSP, Mr Alex‘);
26 INSERT INTO party VALUES (‘SSP‘,‘Scottish Socialist Party‘,NULL);
27 INSERT INTO party VALUES (‘SWP‘,‘Socialist Workers Party‘,NULL);
28 
29 SELECT * FROM party;
30 SELECT * FROM msp;
31 
32 -- 找出没有政党的议员
33 SELECT mspName FROM msp WHERE party IS NULL;
34 
35 -- 列出所有的政党和领导者
36 SELECT partyName,leader FROM party;
37 
38 -- 列出所有有领导者的政党
39 SELECT partyName FROM party WHERE leader IS NOT NULL;
40 
41 -- 列出至少有一个议员的政党
42 SELECT p.partyName,COUNT(m.mspName) FROM party p,msp m WHERE p.partyCode=m.party GROUP BY p.partyName HAVING COUNT(m.mspName)>0;
43  
44 -- 列出所有议员名字和他们所属政党
45 SELECT p.partyName,m.mspName FROM party p,msp m WHERE p.partyCode=m.party GROUP BY m.mspName;
46 
47 -- 列出所有政党和每个政党议员人数
48 SELECT COUNT(m.mspName),p.partyName FROM party p,msp m WHERE p.partyCode=m.party GROUP BY p.partyName;

以上是数据库操作的实例，希望能以此加深记忆。