在 MySQL 中执行数学运算 IF then ELSE 是否可行?
mysqlmysqli database
要执行数学运算和处理条件，您可以考虑 CASE 语句。让我们首先创建一个表 −
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FruitName varchar(100), FruitPrice int ); Query OK, 0 rows affected (0.26 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(FruitName,FruitPrice) values('Orange',250);
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable(FruitName,FruitPrice) values('Banana',100);
Query OK, 1 row affected (0.05 sec)
mysql> insert into DemoTable(FruitName,FruitPrice) values('Apple',150);
Query OK, 1 row affected (0.05 sec)
mysql> insert into DemoTable(FruitName,FruitPrice) values('Pomegranate',200);
Query OK, 1 row affected (0.10 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
这将产生以下输出 −
+----+-------------+------------+ | Id | FruitName | FruitPrice | +----+-------------+------------+ | 1 | Orange | 250 | | 2 | Banana | 100 | | 3 | Apple | 150 | | 4 | Pomegranate | 200 | +----+-------------+------------+ 4 rows in set (0.19 sec)
以下是带有数学运算的 CASE 语句的查询 −
mysql> select Id,FruitName,FruitPrice, case when FruitName='Orange' then FruitPrice/5 else FruitPrice end as OriginalPrice from DemoTable;
这将产生以下输出 −
+----+-------------+------------+---------------+ | Id | FruitName | FruitPrice | OriginalPrice | +----+-------------+------------+---------------+ | 1 | Orange | 250 | 50.0000 | | 2 | Banana | 100 | 100 | | 3 | Apple | 150 | 150 | | 4 | Pomegranate | 200 | 200 | +----+-------------+------------+---------------+ 4 rows in set (0.00 sec)
