PL/SQL關係運算符

關係運算符

關係運算符比較兩個表達式或值，並返回一個布爾結果。下表列出了所有PL/SQL支持的關係運算符。假設變量A=10，變量B=20，則：

運算符

描述

示例

=

檢查兩個操作數的值是否相等，如果是的話那麼條件爲真。

(A = B) 結果爲 false.

!=
<>
~=

檢查兩個操作數的值是否相等，如果值不相等，則條件變爲真。

(A != B) 結果爲 true.

>

檢查左邊的操作數的值是否大於右操作數的值，如果是的話那麼條件爲真。

(A > B) 結果爲 false.

<

檢查左邊的操作數的值是否小於右操作數的值，如果是的話那麼條件爲真。

(A < B) 結果爲 true.

>=

檢查左邊的操作數的值是否大於或等於右操作數的值，如果是的話那麼條件爲真。

(A >= B)  結果爲 false.

<=

檢查左邊的操作數的值是否小於或等於右操作數的值，如果是的話那麼條件爲真。

(A <= B) 結果爲 true.

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; /

當上述代碼在SQL提示符執行時，它產生了以下結果：

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