数据库操作实例

数据库操作实例

DROP TABLE msp;
DROP TABLE party;

CREATE TABLE party (partyCode VARCHAR(10) NOT NULL
                    ,partyName VARCHAR(50)
            ,leader VARCHAR(50)
            ,PRIMARY KEY (partyCode)
            )DEFAULT CHARSET=utf8;
    
CREATE TABLE msp (mspName VARCHAR(50) NOT NULL
                  ,party VARCHAR(10)
          ,constituency VARCHAR(50)
                  ,PRIMARY KEY (mspName)
                  ,FOREIGN KEY (party) REFERENCES party(partyCode)
                  )DEFAULT CHARSET=utf8;

CREATE INDEX msp_party ON msp(party);

INSERT INTO party VALUES ('Com','Communist',NULL);
INSERT INTO party VALUES ('Con','Conservative','McLetchie MSP, David');
INSERT INTO party VALUES ('Green','Green',NULL);
INSERT INTO party VALUES ('Lab','Labour','Dewar MSP, Rt Hon Donald');
INSERT INTO party VALUES ('LD','Liberal Democrat','Wallace QC MSP, Mr Jim');
INSERT INTO party VALUES ('NLP','Natural Law Party',NULL);
INSERT INTO party VALUES ('SNP','Scottish National Party','Salmond MSP, Mr Alex');
INSERT INTO party VALUES ('SSP','Scottish Socialist Party',NULL);
INSERT INTO party VALUES ('SWP','Socialist Workers Party',NULL);

SELECT * FROM party;
SELECT * FROM msp;

-- 找出没有政党的议员
SELECT mspName FROM msp WHERE party IS NULL;

-- 列出所有的政党和领导者
SELECT partyName,leader FROM party;

-- 列出所有有领导者的政党
SELECT partyName FROM party WHERE leader IS NOT NULL;

-- 列出至少有一个议员的政党
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;
 
-- 列出所有议员名字和他们所属政党
SELECT p.partyName,m.mspName FROM party p,msp m WHERE p.partyCode=m.party GROUP BY m.mspName;

-- 列出所有政党和每个政党议员人数
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。