關(guān)系運(yùn)算符比較兩個(gè)表達(dá)式或值,并返回一個(gè)布爾結(jié)果。下表列出了所有PL/SQL支持的關(guān)系運(yùn)算符。假設(shè)變量A=10,變量B=20,則:
運(yùn)算符 | 描述 | 示例 |
---|---|---|
= | 檢查兩個(gè)操作數(shù)的值是否相等,如果是的話那么條件為真。 | (A = B) 結(jié)果為 false. |
!= <> ~= |
檢查兩個(gè)操作數(shù)的值是否相等,如果值不相等,則條件變?yōu)檎妗?/td> | (A != B) 結(jié)果為 true. |
> | 檢查左邊的操作數(shù)的值是否大于右操作數(shù)的值,如果是的話那么條件為真。 | (A > B) 結(jié)果為 false. |
< | 檢查左邊的操作數(shù)的值是否小于右操作數(shù)的值,如果是的話那么條件為真。 | (A < B) 結(jié)果為 true. |
>= | 檢查左邊的操作數(shù)的值是否大于或等于右操作數(shù)的值,如果是的話那么條件為真。 | (A >= B) 結(jié)果為 false. |
<= | 檢查左邊的操作數(shù)的值是否小于或等于右操作數(shù)的值,如果是的話那么條件為真。 | (A <= B) 結(jié)果為 true. |
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(dāng)上述代碼在SQL提示符執(zhí)行時(shí),它產(chǎn)生了以下結(jié)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