【PL/SQL练习】控制结构

1.if判断：

if-then-end if：

SQL> declare
  2
  3   v_ename emp.ename%type;
  4   v_sal  emp.sal%type;
  5
  6  begin
  7
  8   select ename,sal into v_ename,v_sal from emp where empno=&#
  9   dbms_output.put_line('Old salary is: '||v_sal);
 10    if v_sal < 8000 then
 11       update emp set sal=sal+1000 where empno=&num;
 12       commit;
 13    end if;
 14   select ename,sal into v_ename,v_sal from emp where empno=&num;
 15       dbms_output.put_line('New salary is: '||v_sal);
 16
 17  end;

if-then-else-end if：

SQL> declare
  2
  3   v_ename emp.ename%type;
  4   v_sal  emp.sal%type;
  5
  6  begin
  7
  8   select ename,sal into v_ename,v_sal from emp where empno=&#
  9   dbms_output.put_line('Old salary is: '||v_sal);
 10    if v_sal < 8000 then
 11       update emp set sal=sal+1000 where empno=&num;
 12       commit;
 13    else
 14       update emp set sal=sal+500 where empno=&num;
 15       commit;
 16    end if;
 17   select ename,sal into v_ename,v_sal from emp where empno=&num;
 18       dbms_output.put_line('New salary is: '||v_sal);
 19
 20  end;

if-then-elsif-else-end if：

SQL> declare
  2
  3   v_ename emp.ename%type;
  4   v_sal  emp.sal%type;
  5   v_job  emp.job%type;
  6
  7  begin
  8
  9   select ename,job,sal into v_ename,v_job,v_sal from emp where empno=&#
 10   dbms_output.put_line('JOB is: '||v_job||';'||'Old salary is: '||v_sal);
 11    if  v_job='SALESMAN' then
 12       update emp set sal=sal+1000 where empno=#
 13       commit;
 14    elsif  v_job='CLERK' then
 15        update emp set sal=sal+800 where empno=#
 16       commit;
 17    else
 18       update emp set sal=sal+500 where empno=#
 19       commit;
 20    end if;
 21   select ename,job,sal into v_ename,v_job,v_sal from emp where empno=#
 22       dbms_output.put_line('JOB is: '||v_job||';'||'New salary is: '||v_sal);
 23
 24  end;

SQL> declare
  2
  3   v_ename emp.ename%type;
  4   v_sal  emp.sal%type;
  5   v_job  emp.job%type;
  6
  7  begin
  8
  9   select ename,job,sal into v_ename,v_job,v_sal from emp where empno=&#
 10   dbms_output.put_line('JOB is: '||v_job||';'||'Old salary is: '||v_sal);
 11    if  v_job='SALESMAN' then
 12       update emp set sal=sal+1000 where empno=#
 13       commit;
 14    elsif  v_job='CLERK' then
 15        update emp set sal=sal+800 where empno=#
 16       commit;
 17    else
 18       update emp set sal=sal+500 where empno=#
 19       commit;
 20    end if;
 21   select ename,job,sal into v_ename,v_job,v_sal from emp where empno=#
 22       dbms_output.put_line('JOB is: '||v_job||';'||'New salary is: '||v_sal);
 23
 24  end;

2.case分支判断：

SQL> declare
  2      v_ename emp.ename%type;
  3      v_job emp.job%type;
  4      v_sal emp.sal%type;
  5      v_out varchar2(10);
  6
  7     begin
  8       select ename,job,sal into v_ename,v_job,v_sal from emp where empno=&#
  9       dbms_output.put_line('JOB is: '||v_job||';'||'Old salary is: '||v_sal);
 10
 11       v_out:=case v_job
 12           when 'CLERK' THEN v_SAL+100
 13           WHEN 'SALESMAN' THEN v_SAL+200
 14      END ;
 15        select ename,job,sal into v_ename,v_job,v_sal from emp where empno=#
 16        dbms_output.put_line('JOB is: '||v_job||';'||'New salary is: '||v_OUT);
 17         dbms_output.put_line(v_out);
 18     end;

SQL> declare
  2      v_ename emp.ename%type;
  3      v_job emp.job%type;
  4      v_sal emp.sal%type;
  5      v_out varchar2(10);
  6
  7     begin
  8       select ename,job,sal into v_ename,v_job,v_sal from emp where empno=&#
  9       dbms_output.put_line('JOB is: '||v_job||';'||'Old salary is: '||v_sal);
 10
 11       v_out:=case v_job
 12           when 'CLERK' THEN v_SAL+100
 13           WHEN 'SALESMAN' THEN v_SAL+200
 14      END ;
 15        select ename,job,sal into v_ename,v_job,v_sal from emp where empno=#
 16        dbms_output.put_line('JOB is: '||v_job||';'||'New salary is: '||v_OUT);
 17
 18     end;

SQL> declare
  2      v_ename emp.ename%type;
  3      v_job emp.job%type;
  4      v_sal emp.sal%type;
  5      v_out varchar2(10);
  6
  7     begin
  8       select ename,job,sal into v_ename,v_job,v_sal from emp where empno=&#
  9       dbms_output.put_line('JOB is: '||v_job||';'||'Old salary is: '||v_sal);
 10
 11       v_out:=case v_job
 12           when 'CLERK' THEN v_SAL+100
 13           WHEN 'SALESMAN' THEN v_SAL+200
 14      END ;
 15        select ename,job,sal into v_ename,v_job,v_sal from emp where empno=#
 16        dbms_output.put_line('JOB is: '||v_job||';'||'New salary is: '||v_OUT);
 17
 18     end;

在sql中使用case：

SQL>  select ename,job,sal,
  2      CASE
  3     WHEN JOB='CLERK' THEN SAL+100
  4     WHEN JOB='MANAGER' THEN SAL+50
  5     WHEN JOB='SALESMAN' THEN SAL+300
  6     ELSE
  7      SAL
  8    END AS ADD_SAL
  9     FROM EMP;

decode 语句：

SQL> select ename,sal,JOB,
  2          decode (job ,'CLERK',SAL+100,
  3                        'SALESMAN',SAL+300,
  4                         'MANAGER',SAL+50,
  5                         SAL) ADD_SAL
  6        FROM EMP;

3.循环语句：

案例：在表中插入数据

①loop基本循环

SQL> declare
  2  v_num number :=1;
  3  v_count number;
  4
  5  begin
  6
  7   loop
  8       insert into t1 values (v_num,'tom'||v_num ,'ok');
  9        v_num :=v_num + 1;
 10
 11   exit when v_num >10;
 12
 13   end loop;
 14   commit;
 15
 16   select count(*) into v_count from t1;
 17
 18   dbms_output.put_line('T1 rows is :'||v_count);
 19
 20  end;

②for 循环：

SQL> declare
  2  v_count number;
  3
  4  begin
  5
  6  for i in 1..10
  7    loop
  8       insert into t1 values (i,'tom'||i ,'ok');
  9   end loop;
 10   commit;
 11
 12   select count(*) into v_count from t1;
 13
 14   dbms_output.put_line('T1 rows is :'||v_count);
 15
 16  end;

③while 循环：

SQL> declare
  2  v_num number := 1;
  3  v_count number  ;
  4
  5  begin
  6
  7   while v_num <=10 loop
  8       insert into t1 values (v_num,'tom'||v_num ,'ok');
  9       v_num := v_num + 1;
 10   end loop;
 11   commit;
 12
 13   select count(*) into v_count from t1;
 14
 15   dbms_output.put_line('T1 rows is :'||v_count);
 16
 17  end;