括号在MySQL SELECT(COLNAME)中是什么意思？
SELECT(COLNAME)表示，我们正在为该列创建别名。让我们看一个例子并创建一个表-
mysql> create table DemoTable865( FirstName varchar(100), LastName varchar(100) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable865 values('Chris','Brown');
mysql> insert into DemoTable865 values('Adam','Smith');
mysql> insert into DemoTable865 values('David','Miller');
mysql> insert into DemoTable865 values('Carol','Taylor');使用select语句显示表中的所有记录-
mysql> select *from DemoTable865;
这将产生以下输出-
+-----------+----------+ | FirstName | LastName | +-----------+----------+ | Chris | Brown | | Adam | Smith | | David | Miller | | Carol | Taylor | +-----------+----------+ 4 rows in set (0.00 sec)
在这里，我们使用SELECT(COLNAME)MySQL为列创建别名-
mysql> select (FirstName) StudentFirstName,(LastName) StudentLastName from DemoTable865;
这将产生以下输出-
+------------------+-----------------+ | StudentFirstName | StudentLastName | +------------------+-----------------+ | Chris | Brown | | Adam | Smith | | David | Miller | | Carol | Taylor | +------------------+-----------------+ 4 rows in set (0.00 sec)