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  • Oracle 增删列,为列增加注释,修改主键等

    DROP TABLE STUDY;
    DROP TABLE STUDENT;
    DROP TABLE COURSE;
    /
    CREATE TABLE  STUDENT
    (
       SID VARCHAR(10),
       SName varchar(30),
       primary key (SID)
    );
    /
    CREATE TABLE COURSE
    (
      CID VARCHAR(10),
      CName varchar(50),
      primary key (CID)
    );
    /

    CREATE TABLE STUDY
    (
      SID  VARCHAR(10),
      CID  VARCHAR(10),
      SCORE INTEGER  DEFAULT 0 CHECK (SCORE between 0 and 100),
      constraint PK_STUDY  PRIMARY KEY (SID)  --注意此处设置主键约束名,便于后面修改表的主键
    );
    /
    COMMIT;
    /

    select * from student;
    select * from study;
    /
    --以表 student,study,score 为例
    --1.增加列
    alter table student  add (sex varchar2(2) DEFAULT '女',age integer,address varchar(100)) ;
    /
    --2.修改列定义
    ALTER TABLE student MODIFY sex VARCHAR2(4)  DEFAULT '男';
    /
    --3.删除列
    ALTER TABLE student DROP COLUMN address;
    /
    --4.修改列名
    ALTER TABLE student RENAME COLUMN   sid to sno;
    /
    ALTER TABLE student RENAME COLUMN   sno to sid;
    /
    --5.修改表名
    RENAME study TO Learn;
    /
    RENAME Learn TO study;
    /
    --6.增加注释
    -- 给表添加释
    COMMENT ON TABLE STUDY IS '学习信息表';
    /
    --给列添加注释
    COMMENT ON COLUMN STUDY.SID IS '学员编号';
    /
    --7.增加外键关联
    ALTER TABLE study ADD CONSTRAINT FK_study_R_student_S FOREIGN KEY (SID) REFERENCES  student(SID);

    /
    --8.修改主键
    --查找主键约束名
    select T.constraint_name from USER_CONSTRAINTS T where table_name='STUDY' and constraint_type='P' AND ROWNUM<2;
    /
    --删除主键约束
    ALTER TABLE study DROP CONSTRAINT  PK_STUDY 
    /  
    --添加主键
    alter table study add constraint PK_STUDY  primary key (cid,sid); 
    /
    commit;
    /

    select * from student;
    select * from study;
    select * from COURSE;
    /

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  • 原文地址:https://www.cnblogs.com/furenjun/p/oracleColumn.html
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