在MySQL中的日期之间有条件地选择表中设置的价格的最大值和最小值？
您需要使用CASE语句有条件地在日期之间进行选择，以找到最低和最高价格。用聚合函数MIN()和结束CASE语句MAX()。语法如下：
SELECT MIN(CASE WHEN CURDATE() BETWEEN yourStartDateColumnName AND yourEndDateColumnName THEN yourLowPriceColumnName ELSE yourHighPriceColumnName END) AS anyVariableName, MAX(CASE WHEN CURDATE() BETWEEN yourStartDateColumnName AND yourEndDateColumnName THEN yourLowPriceColumnName ELSE yourHighPriceColumnName END) AS anyVariableName FROM yourTableName;
为了理解上述语法，让我们创建一个表。创建表的查询如下：
mysql> create table ConditionalSelect -> ( -> Id int NOT NULL AUTO_INCREMENT, -> StartDate datetime, -> EndDate datetime, -> LowerPrice int, -> HigherPrice int, -> PRIMARY KEY(Id) -> );
使用insert命令在表中插入一些记录。查询如下：
mysql> insert into ConditionalSelect(StartDate,EndDate,LowerPrice,HigherPrice) values('2019-01-02','2019-04-02',5,10);
mysql> insert into ConditionalSelect(StartDate,EndDate,LowerPrice,HigherPrice) values('2019-04-02','2019-04-20',0,20);
mysql> insert into ConditionalSelect(StartDate,EndDate,LowerPrice,HigherPrice) values('2019-04-03','2019-04-21',0,30);使用select语句显示表中的所有记录。查询如下：
mysql> select *from ConditionalSelect;
以下是输出：
+----+---------------------+---------------------+------------+-------------+ | Id | StartDate | EndDate | LowerPrice | HigherPrice | +----+---------------------+---------------------+------------+-------------+ | 1 | 2019-01-02 00:00:00 | 2019-04-02 00:00:00 | 5 | 10 | | 2 | 2019-04-02 00:00:00 | 2019-04-20 00:00:00 | 0 | 20 | | 3 | 2019-04-03 00:00:00 | 2019-04-21 00:00:00 | 0 | 30 | +----+---------------------+---------------------+------------+-------------+ 3 rows in set (0.00 sec)
这是在日期之间选择最低和最高价格的查询：
mysql> SELECT -> MIN(CASE WHEN CURDATE() BETWEEN StartDate AND EndDate THEN LowerPrice ELSE HigherPrice END) AS MinimumValue, -> MAX(CASE WHEN CURDATE() BETWEEN StartDate AND EndDate THEN LowerPrice ELSE HigherPrice END) AS MaximumValue -> from ConditionalSelect;
以下是输出：
+--------------+--------------+ | MinimumValue | MaximumValue | +--------------+--------------+ | 5 | 30 | +--------------+--------------+ 1 row in set (0.00 sec)