如何使用MySQL从同一列中选择不同的值并在不同的列中显示它们？
要根据条件选择不同的值，请使用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, Name varchar(40), Score int ) ;
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(Name,Score) values('Chris',45);
mysql> insert into DemoTable(Name,Score) values('David',68);
mysql> insert into DemoTable(Name,Score) values('Robert',89);
mysql> insert into DemoTable(Name,Score) values('Bob',34);
mysql> insert into DemoTable(Name,Score) values('Sam',66);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 | Name | Score | +----+--------+-------+ | 1 | Chris | 45 | | 2 | David | 68 | | 3 | Robert | 89 | | 4 | Bob | 34 | | 5 | Sam | 66 | +----+--------+-------+ 5 rows in set (0.00 sec)
以下是从同一列中选择不同值的查询-
mysql> select Score, case when Score < 40 then Score end as ' Score Less than 40', case when Score between 60 and 70 then Score end as 'Score Between 60 and 70 ', case when Score > 80 then Score end as 'Score greater than 80' from DemoTable;
这将产生以下输出-
+-------+--------------------+--------------------------+-----------------------+ | Score | Score Less than 40 | Score Between 60 and 70 | Score greater than 80 | +-------+--------------------+--------------------------+-----------------------+ | 45 | NULL | NULL | NULL | | 68 | NULL | 68 | NULL | | 89 | NULL | NULL | 89 | | 34 | 34 | NULL | NULL | | 66 | NULL | 66 | NULL | +-------+--------------------+--------------------------+-----------------------+ 5 rows in set, 1 warning (0.03 sec)