PL/SQL关系运算符

关系运算符比较两个表达式或值,并返回一个布尔结果。 下表显示了PL/SQL支持的所有关系运算符。假设变量A=10,变量B=20,则 –

关系运算符示例

运算符 示例 示例
= 检查两个操作数的值是否相等,如果是,则条件成立。 (A = B)为假
!=,<>~= 检查两个操作数的值是否相等,如果两个值不相等则条件成为真。 (A != B)为真
> 检查左操作数的值是否大于右操作数的值,如果是,则条件成为真。 (A > B) 为假
< 检查左操作数的值是否小于右操作数的值,如果是,则条件成为真。 (A < B) 条件为真。
>= 检查左操作数的值是否大于或等于右操作数的值,如果是,则条件成为真。 (A >= B) 为假
<= 检查左操作数的值是否小于或等于右操作数的值,如果是,则条件成为真。 (A <= B) 为真

示例

DECLARE 
   a number (2) := 21; 
   b number (2) := 10; 
BEGIN 
   IF (a = b) then 
      dbms_output.put_line('Line 1 - a is equal to b'); 
   ELSE 
      dbms_output.put_line('Line 1 - a is not equal to b'); 
   END IF;  
   IF (a < b) then 
      dbms_output.put_line('Line 2 - a is less than b'); 
   ELSE 
      dbms_output.put_line('Line 2 - a is not less than b'); 
   END IF; 

   IF ( a > b ) THEN 
      dbms_output.put_line('Line 3 - a is greater than b'); 
   ELSE 
      dbms_output.put_line('Line 3 - a is not greater than b'); 
   END IF;  
   -- Lets change value of a and b 
   a := 5; 
   b := 20; 
   IF ( a <= b ) THEN 
      dbms_output.put_line('Line 4 - a is either equal or less than b'); 
   END IF; 
   IF ( b >= a ) THEN 
      dbms_output.put_line('Line 5 - b is either equal or greater than a'); 
   END IF;
   IF ( a <> b ) THEN 
      dbms_output.put_line('Line 6 - a is not equal to b'); 
   ELSE 
      dbms_output.put_line('Line 6 - a is equal to b'); 
   END IF;  
END; 
/

当上述代码在SQL提示下执行后,会产生以下结果 –

Line 1 - a is not equal to b 
Line 2 - a is not less than b 
Line 3 - a is greater than b 
Line 4 - a is either equal or less than b 
Line 5 - b is either equal or greater than a 
Line 6 - a is not equal to b  

PL/SQL procedure successfully completed

    原文作者:PL/SQL教程
    原文地址: https://www.yiibai.com/plsql/plsql_relational_operators.html
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