zoukankan      html  css  js  c++  java
  • Oracle Auto Increment Column

     
     

    Solution 1: Prior to Oracle 11g, sequence assignment to a number variable could be done through a SELECT statement only in trigger, which requires context switching from PL/SQL engine to SQL engine. So we need to create before insert trigger for each row, and assign sequence new value to the column using select into clause.

    create table test_tab
    (
        id number primary key
    );
    
    create sequence test_seq start with 1 increment by 1 nocycle;
    
    create or replace trigger test_trg 
    before insert on test_tab 
    for each row 
    begin
        select test_seq.nextval into :new.id
        from dual;
    end;
    /
    

    Solution 2: From Oracle 11g, we can directly assign a sequence value to a pl/sql variable in trigger, So we can create before insert trigger for each row, and assign sequence nextval to the column directly.

    create table test_tab
    (
        id number primary key
    );
    
    create sequence test_seq start with 1 increment by 1 nocycle;
    
    create or replace trigger test_trg 
    before insert on test_tab 
    for each row 
    begin
        :new.id := test_seq.nextval;
    end;
    /
    

    Solution 3: With Oracle 12c, we can directly assign sequence nextval as a default value for a column, So you no longer need to create a trigger to populate the column with the next value of sequence, you just need to declare it with table definition.

    create sequence test_seq start with 1 increment by 1 nocycle;
    
    create table test_tab
    (
        id number default test_seq.nextval primary key
    );
    
     
  • 相关阅读:
    unity3d应用内分享(微信、微博等)的实现
    Cocostudio 文章列表
    C++ 文章列表
    Android 文章列表
    js函数节流和函数防抖
    js实现队列-通过闭包方式
    初学js正则
    Android网络图片加载
    利用html5制作正方体,同时实现3D旋转效果
    Python模块——random随机模块
  • 原文地址:https://www.cnblogs.com/kramer/p/3518741.html
Copyright © 2011-2022 走看看