在 MySQL UNION 中保留选择顺序?
mysqlmysqli database
使用 CASE 语句是个不错的选择。不要使用 UNION。让我们先创建一个表 −
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, ShippingDate datetime ); Query OK, 0 rows affected (0.63 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(ShippingDate) values('2019-04-21');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable(ShippingDate) values('2019-01-01');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable(ShippingDate) values('2019-05-11');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable(ShippingDate) values('2018-12-31');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable(ShippingDate) values('2019-02-18');
Query OK, 1 row affected (0.19 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 | ShippingDate | +----+---------------------+ | 1 | 2019-04-21 00:00:00 | | 2 | 2019-01-01 00:00:00 | | 3 | 2019-05-11 00:00:00 | | 4 | 2018-12-31 00:00:00 | | 5 | 2019-02-18 00:00:00 | +----+---------------------+ 5 rows in set (0.00 sec)
以下是使用 order by case 保留选择顺序的查询。
mysql> select *from DemoTable ORDER BY CASE WHEN ShippingDate < CURDATE() THEN ShippingDate ELSE CURDATE() END DESC, ShippingDate ASC;
这将产生以下输出 −
+----+---------------------+ | Id | ShippingDate | +----+---------------------+ | 3 | 2019-05-11 00:00:00 | | 1 | 2019-04-21 00:00:00 | | 5 | 2019-02-18 00:00:00 | | 2 | 2019-01-01 00:00:00 | | 4 | 2018-12-31 00:00:00 | +----+---------------------+ 5 rows in set (0.00 sec)
