pl/sql 实例精解 04

本章主要讨论, IF 语句的应用.

   1:  if condition1 then

   2:    statement1

   3:  elsif condition2 then

   4:    statement2

   5:  else

   6:    statement3

   7:  end if;

注意: := 用于 PL/SQL 块的赋值操作, = 一般用于 SQL 的赋值操作

   1:  set serveroutput on

   2:   

   3:  declare

   4:      v_student_id    number := 102;

   5:      v_section_id    number := 89;

   6:      v_final_grade    number;

   7:      v_letter_grade    char(1);

   8:  begin

   9:      select final_grade

  10:        into v_final_grade

  11:        from enrollment

  12:       where student_id = v_student_id

  13:         and section_id = v_section_id;

  14:         

  15:      if v_final_grade between 90 and 100 then

  16:          v_letter_grade := 'A';

  17:      elsif v_final_grade between 80 and 89 then

  18:          v_letter_grade := 'B';

  19:      else

  20:          v_letter_grade := 'C';

  21:      end if;

  22:      

  23:      dbms_output.put_line('Letter grade is: ' || v_letter_grade);

  24:  end;

  25:  /

  26:  show errors;

另外, 还可以使用嵌套的 IF 语句, 及逻辑操作符 and , or, not