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Legal StudiesTernary operation 是否像 C 或 C++ 一樣在 MySQL 中存在？
對，讓我們首先檢視 C 或 C++ 語言中三元運算子的工作原理。
X=(X > 10 && ( X-Y) < 0) ?: X:(X-Y);
以下是 C 語言中的演示程式碼。之後，我們將檢查 MySQL。C 程式碼如下所示 −
#include <stdio.h>
int main() {
int X;
int Y;
int result;
printf("Enter the value for X:");
scanf("%d",&X);
printf("Enter the value for Y:");
scanf("%d",&Y);
result=( X > 1 && (X-Y) < 0) ? X: (X-Y);
printf("The Result is=%d",result);
return 0;
}C 程式碼的快照如下 −
以下是輸出 −
MySQL 三元運算子的語法如下 −
select case when yourtableAliasName.yourColumnName1 > 1 AND (yourtableAliasName.yourColumnName1-yourtableAliasName.yourColumnName2) < 0 THEN 0 ELSE (yourtableAliasName.yourColumnName1-yourtableAliasName.yourColumnName2) END AS anyAliasName from yourTableName yourtableAliasName;
為了理解以上三元運算子語法，讓我們建立一個表。建立表的查詢如下 −
mysql> create table TernaryOperationDemo -> ( -> X int, -> Y int -> ); Query OK, 0 rows affected (0.61 sec)
使用 insert 命令向表中插入一些記錄。查詢如下 −
mysql> insert into TernaryOperationDemo values(10,5); Query OK, 1 row affected (0.14 sec) mysql> insert into TernaryOperationDemo values(5,15); Query OK, 1 row affected (0.16 sec) mysql> insert into TernaryOperationDemo values(20,15); Query OK, 1 row affected (0.15 sec) mysql> insert into TernaryOperationDemo values(15,25); Query OK, 1 row affected (0.13 sec) mysql> insert into TernaryOperationDemo values(10,-11); Query OK, 1 row affected (0.15 sec)
使用 select 語句顯示錶中的所有記錄 −
mysql> select *from TernaryOperationDemo;
以下是輸出 −
+------+------+ | X | Y | +------+------+ | 10 | 5 | | 5 | 15 | | 20 | 15 | | 15 | 25 | | 10 | -11 | +------+------+ 5 rows in set (0.00 sec)
以下是三元運算子的查詢 −
mysql> select case when tbl.X > 1 AND (tbl.X-tbl.Y) < 0 THEN 0 ELSE (tbl.X-tbl.Y) END AS Result from TernaryOperationDemo tbl;
以下是輸出 −
+--------+ | Result | +--------+ | 5 | | 0 | | 5 | | 0 | | 21 | +--------+ 5 rows in set (0.00 sec)
更新於: 30-7-2019
57 次瀏覽
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