数据库三道简答题 数据库简答题
sql\u6570\u636e\u5e93\u8fd9\u4e09\u9053\u9898\u5e94\u8be5\u600e\u4e48\u505a\uff1f\u6ce8\u610f\uff1a\u5c0f\u5199\u7684\u5b57\u6bcd\u4e3a\u8868\u7684\u522b\u547d\u540d\uff0c\u5b57\u6bb5\u5927\u5c0f\u5199\u6ca1\u6709\u533a\u5206\uff0c\u4f60\u8981\u662f\u533a\u5206\u7684\u8bdd\u533a\u5206\u4e0b\uff0csql \u67e5\u8be2\u5668\u91cc\u9762\u53ef\u4ee5\u8bbe\u7f6e
\u67e5\u8be2\u8ba2\u5355\u91d1\u989d\u6700\u9ad8\u7684\u5ba2\u6237\u540d\u3001\u8d27\u54c1\u540d\u79f0\u3001\u8d2d\u4e70\u6570\u91cf\u3001\u91d1\u989d\u548c\u4e0b\u5355\u65f6\u95f4\u3002
select c.cname \u5ba2\u6237\u540d ,p.pname \u8d27\u54c1\u540d\u79f0,o.quantity \u8d2d\u4e70\u6570\u91cf,max(o.money) \u91d1\u989d\uff0co.orderdate \u4e0b\u5355\u65f6\u95f4
from Customer c,Product p, Orders o
where c.cid=o.cid and o.oid=p.pid
2.\u67e5\u8be2\u5e93\u5b58\u91cf\u4f4e\u4e8e10\u7684\u5546\u54c1\u540d\u79f0
select p.pname \u8d27\u54c1\u540d\u79f0
from Product p
where p.quantity<10
3.
\u5047\u8bbe\u8ba2\u5355\u8868Orders\u5df2\u521b\u5efa\uff0c\u4e3a\u8be5\u8868\u6dfb\u52a0\u9ed8\u8ba4\u503c\u7ea6\u675f\uff0c\u8ba2\u5355\u65e5\u671f\u4e3a\u5f53\u524d\u65e5\u671f
Alter table Orders Alter Column \u8ba2\u5355\u65e5\u671f datetime default getdate()
Insert into student ('number','name','age','sex') value ('1','\u5f20\u4e09'\uff0c'18','1');
\u683c\u5f0f insert into \u8868\u540d (\u5217\u540d) value (\u503c)
数据模型的三要素
1、概念数据模型（Conceptual Data Model）
2、逻辑数据模型（Logical Data Model）
3、物理数据模型（Physical Data Model）
自己找书展开
2.delete是删除记录操作,如果数据有日志,在删除的同时会记录在日志中,drop table 是删除整个表机构,比如一个几百万行带日志库表,你用delete删除这个表可能要花几十分钟来写日志,如果你用drop talbe只是瞬间的事
3. on delete cascade
on delete no action
on delete set null
对应完整性应对方式,具体应用网络查看资料
基础的概念题,楼上各位很不专业啊
1。有ER模型和类模型
2。delete是删除表，drop table是修改表
3。基本表约束，断言，域定义
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绛旓細CREATE TABLE 鐮旂┒浜哄憳 (浜哄憳缂栧彿 int PRIMARY KEY, 濮撳悕 CHAR(8), 骞撮緞 SMALLINT CHECK(骞撮緞<=35), 鑱岀О CHAR(8) CHECK(鑱岀О IN(鈥樿甯堚,鈥樺壇鏁欐巿鈥,鈥樻暀鎺堚)) ); CREATE TABLE 椤圭洰 (椤圭洰缂栧彿 int PRIMARY KEY, 鍚嶇О CHAR(20), 璐熻矗浜虹紪鍙 INT, 绫诲埆 CHAR(8), FOREIGN KEY(璐熻矗浜...
绛旓細where a.cno = '1' --鏁版嵁搴 璇剧▼浠ｇ爜 group by b.Sdept --3銆佹煡璇㈣嚦灏戦変慨浜嗗鐢焥1閫変慨鐨勫叏閮ㄨ绋嬬殑瀛︾敓鍙风爜 select distinct a.Sno from SC a where a.Sno <> '001' --浠001浠ｈ〃瀛︾敓S1鐨勭紪鍙 and not exists (select from SC b where b.Sno = '001'and not exists (select 1 f...
绛旓細瀵逛笉璧凤紝涓嶄細
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