Oracle creates B-trees, reverses, bitmap indexes, declares variables, process control (judgment), catches exceptions, opens cursors, stored procedures, and passes parameters

learning target

1. Master JAVA entry to advanced knowledge in one week ( continuous writing... )
2. Master basic C# l window knowledge ( creating... )
3. Teach you how to make vbs scripts ( complete... )
4. Powerful IDEA programming tool ( written in ...... )
5, the classic common interview questions skills ( update ...... )

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Preface

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Hope: In the new year of 2021, you will have everything you want and let it go!

Create index

SELECT * FROM STUDENT WHERE SSEX='男'
-- 创建B树索引
CREATE INDEX index_id ON STUDENT(SID)
--删除索引
DROP INDEX index_id
--创建反向键索引
CREATE INDEX index_reverse_id ON STUDENT(SID) REVERSE
-- 创建位图索引
CREATE BITMAP INDEX index_bit_sex ON STUDENT(SSEX)
drop INDEX index_bit_sex

Declare variable

声明变量
declare 
     v_name varchar2(50):='男神';
     -- 把student表中sex字段的数据类型作为当前变量的数据类型
     v_sex STUDENT.SSEX%type;
begin
  -- 第一种赋值方式
  v_name:='男神';
  -- 输出语句
  dbms_output.put_line(v_name);
  -- 第二种赋值方式，把表中的某条数据赋值到变量中
  SELECT SNAME,SSEX INTO v_name,v_sex FROM STUDENT WHERE SID=10;
  dbms_output.put_line(v_name||'-'||v_sex);
end;

Process control (judgment)

- 流程控制（判断）
declare
   v_score number:=90;
   v_remark varchar2(50);
begin
  case --判断开始
    --when 判断 then 满足条件后执行;
    when v_score=100 then v_remark:='满分';
    when v_score>=80 then v_remark:='优秀';
    when v_score>=60 then v_remark:='及格';
    else --如果前面的条件都不符合就进入else
        v_remark:='不及格';
  end case;--判断结束  
  dbms_output.put_line(v_remark);

Catch exception

-- 捕获异常
  -- exception
   -- when 需要捕获的异常类型 then 如果发生该异常怎么处理;
  exception
    when ACCESS_INTO_NULL then dbms_output.put_line('报错了');
end;
--游标，类似于java jdbc查询后的结果集，可以保存一条sql的查询结果
declare
    v_name STUDENT.SNAME%TYPE;
    -- cursor(定义游标关键字) 游标名称 IS 查询语句
    cursor cursor_sname IS SELECT SNAME FROM STUDENT;
 begin
   --打开游标
   open cursor_sname;
   loop
        --循环游标把每次获取到的值放到变量中
        fetch cursor_sname into v_name;
        --循环的退出条件
        --cursor_sname%NOTFOUND游标中是否还存在下一个数据
        exit when cursor_sname%NOTFOUND;
        dbms_output.put_line(v_name);
   end loop;
 end;

Stored procedure

--存储过程，类似java中的方法，Java可以通过存储过程名称调用已经定义好的存储过程
 --创建或者修改存储过程
 CREATE OR REPLACE PROCEDURE add_student(
        --参数，输入参数和输出参数
        v_sname varchar2,
        v_ssex varchar2,
        v_sage out number 
 )
 is
 begin
   insert into student values(STU_ID.Nextval,v_sname,v_ssex,v_sage);
 end; 
declare  
 v_xxxx varchar2(50);
begin
 -- 按照顺序传参
 add_student('小三角','女',v_xxxx);
 
 -- 按照参数名称传值
 add_student(v_ssex=>'男',v_sage=>11,v_sname=>'dsadsa');
 
 commit;
end;

SELECT * FROM STUDENT

to sum up

Learning Oracle is a long and arduous process. If you have no interest but are forced to learn, then it is difficult to learn well. To summarize briefly, it is: interest, learning and practice.