如何使用 MySQL 查询连接来自不同列的字符串和附加字符串?
mysqlmysqli database
首先我们创建一个表 −
mysql> create table DemoTable ( FirstName varchar(100), LastName varchar(100) ); Query OK, 0 rows affected (0.76 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable values('Chris','Brown');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('Adam','Smith');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values('Carol','Taylor');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable values('David','Miller');
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 DemoTable;
这将产生以下输出 −
+-----------+----------+ | FirstName | LastName | +-----------+----------+ | Chris | Brown | | Adam | Smith | | Carol | Taylor | | David | Miller | +-----------+----------+ 4 rows in set (0.00 sec)
以下是执行连接的查询。这里，我们有 FirstName 和 LastName。此外，还会在开头为所有字符串值连接一个附加字符串 −
mysql> select concat('Hello ',FirstName,' ',LastName) from DemoTable;
这将产生以下输出 −
+-----------------------------------------+
| concat('Hello ',FirstName,' ',LastName) |
+-----------------------------------------+
| Hello Chris Brown |
| Hello Adam Smith |
| Hello Carol Taylor |
| Hello David Miller |
+-----------------------------------------+
4 rows in set (0.00 sec)
