pl/sql 实例精解 04

本章主要讨论, IF 语句的应用.

if condition1 then
  statement1
elsif condition2 then
  statement2
else
  statement3
end if;

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

set serveroutput on

declare
    v_student_id    number := 102;
    v_section_id    number := 89;
    v_final_grade    number;
    v_letter_grade    char(1);
begin
    select final_grade
      into v_final_grade
      from enrollment
     where student_id = v_student_id
       and section_id = v_section_id;

    if v_final_grade between 90 and 100 then
        v_letter_grade := 'A';
    elsif v_final_grade between 80 and 89 then
        v_letter_grade := 'B';
    else
        v_letter_grade := 'C';
    end if;

    dbms_output.put_line('Letter grade is: ' || v_letter_grade);
end;
/
show errors;

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