MySQL 查询是否只保留列值中的前 2 个字符并删除其余字符?
mysqlmysqli database
要只保留前两个字符并删除其余字符，请使用 SUBSTRING()。
首先我们创建一个表 −
mysql> create table DemoTable743 (SubjectName varchar(100)); Query OK, 0 rows affected (0.54 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable743 values('MySQL');
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable743 values('Java');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable743 values('MongoDB');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable743 values('Python');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable743 values('Data Structure');
Query OK, 1 row affected (0.68 sec)
mysql> insert into DemoTable743 values('Algorithm');
Query OK, 1 row affected (0.12 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable743;
这将产生以下输出 -
+----------------+ | SubjectName | +----------------+ | MySQL | | Java | | MongoDB | | Python | | Data Structure | | Algorithm | +----------------+ 6 rows in set (0.00 sec)
以下查询保留列值中的前 2 个字符并删除其余字符 −
mysql> update DemoTable743 set SubjectName=SUBSTRING(SubjectName,1,2); Query OK, 6 rows affected (0.12 sec) Rows matched: 6 Changed: 6 Warnings: 0
让我们再次检查表记录 −
mysql> select *from DemoTable743;
这将产生以下输出 -
+-------------+ | SubjectName | +-------------+ | My | | Ja | | Mo | | Py | | Da | | Al | +-------------+ 6 rows in set (0.00 sec)
