MySQL SELECT 向查询添加新列并赋予其值?
mysqlmysqli database
要向 MySQL 查询添加列并赋予其值，请使用以下语法 −
select yourColumnName1,yourColumnName2,.....N ,yourValue AS anyAliasName from yourTableName;
首先我们创建一个表 −
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(20) ); Query OK, 0 rows affected (0.84 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(FirstName) values('John');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable(FirstName) values('Larry');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable(FirstName) values('Chris');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable(FirstName) values('Robert');
Query OK, 1 row affected (0.15 sec)
以下是使用 select 语句显示表中的所有记录的查询 −
mysql> select *from DemoTable;
这将产生以下输出 −
+----+-----------+ | Id | FirstName | +----+-----------+ | 1 | John | | 2 | Larry | | 3 | Chris | | 4 | Robert | +----+-----------+ 4 rows in set (0.00 sec)
以下是向 MySQL 添加列并赋予其值的查询。这里我们在创建新列 AGE 后将值设置为 23 −
mysql> select Id,FirstName,23 AS AGE from DemoTable;
这将产生以下输出 −
+----+-----------+-----+ | Id | FirstName | AGE | +----+-----------+-----+ | 1 | John | 23 | | 2 | Larry | 23 | | 3 | Chris | 23 | | 4 | Robert | 23 | +----+-----------+-----+ 4 rows in set (0.00 sec)
