下表列出了所有D語言支持的關係運算符。假設變數A=10和變數B=20，則：
| 運算符 | 描述 | 示例 |
|---|---|---|
| == | 檢查，如果兩個運算元的值相等與否，如果是則條件為真。 | (A == B) is not true. |
| != | 檢查，如果兩個運算元的值相等與否，如果值不相等，則條件變為真。 | (A != B) is true. |
| > | 如果左運算元的值大於右運算元的值，如果是則條件為真檢查。 | (A > B) is not true. |
| < | 如果檢查左運算元的值小於右運算元的值，如果是則條件為真。 | (A < B) is true. |
| >= | 如果左運算元的值大於或等於右運算元的值，如果是則條件為真檢查。 | (A >= B) is not true. |
| <= | 如果檢查左運算元的值小於或等於右運算元的值，如果是則條件為真。 | (A <= B) is true. |
示例
試試下麵的例子就明白了所有的D編程語言的關係運算符：
import std.stdio; int main(string[] args) { int a = 21; int b = 10; int c ; if( a == b ) { writefln("Line 1 - a is equal to b " ); } else { writefln("Line 1 - a is not equal to b " ); } if ( a < b ) { writefln("Line 2 - a is less than b " ); } else { writefln("Line 2 - a is not less than b " ); } if ( a > b ) { printf("Line 3 - a is greater than b " ); } else { writefln("Line 3 - a is not greater than b " ); } /* Lets change value of a and b */ a = 5; b = 20; if ( a <= b ) { printf("Line 4 - a is either less than or equal to b " ); } if ( b >= a ) { writefln("Line 5 - b is either greater than or equal to b " ); } return 0; }
當編譯並執行上面的程式它會產生以下結果：
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 less than or equal to b Line 5 - b is either greater than or equal to b