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Chapter 15 序列号(Sequence)和同义词(Synonym)SQL> desc supplier;Name Type Nullable Default Comments ------- ------------ -------- ------- -------- S_CODE NUMBER(6) Y SNAME VARCHAR2(25) Y CONTACT VARCHAR2(1... 阅读全文
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Chapter 14 View 最基本的表也就是实体是不会发生变化的,变化的应该是视图。create view averageas select d.dname "部门", avg(e.sal) "平均工资", avg(nvl(comm,0)) "平均佣金", count(*) "员工数"from emp e, dept dwhere e.deptno = d.deptnogroup by d.d... 阅读全文
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Chapter 13 索引与约束(Indexes and Constraints)create table empconas select * from emp;select * from empcon;SQL> desc empcon;Name Type Nullable Default Comments -------- ------------ -------- ------- ---... 阅读全文
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Chapter 12 数据的维护数据维护包括了DML (Data Manipulating Language) 数据操作语言和事务控制(Transaction Control).create table emp_dmlasselect * from emp;select *from emp_dml;create table dept_dmlas select * from dept;select ... 阅读全文