如何在单个MySQL查询中添加列和索引？
为此，将ALTER与ADD配合使用。以下是语法-
alter table yourTableName add yourColumnName DATETIME DEFAULT NOW(), add index(yourColumnName);
让我们首先创建一个表-
mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(100), -> PRIMARY KEY(Id) -> );
让我们检查表的描述-
mysql> desc DemoTable;
输出结果
这将产生以下输出-
+-------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+--------------+------+-----+---------+----------------+ | Id | int(11) | NO | PRI | NULL | auto_increment | | Name | varchar(100) | YES | | NULL | | +-------+--------------+------+-----+---------+----------------+ 2 rows in set (0.01 sec)
这是在单个MySQL查询中添加列和索引的查询-
mysql> alter table DemoTable -> add ArrivalDate DATETIME DEFAULT NOW(), -> add index(ArrivalDate); Records: 0 Duplicates: 0 Warnings: 0
让我们再次检查表的描述-
mysql> desc DemoTable;
输出结果
这将产生以下输出-
+-------------+--------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+--------------+------+-----+-------------------+----------------+ | Id | int(11) | NO | PRI | NULL | auto_increment | | Name | varchar(100) | YES | | NULL | | | ArrivalDate | datetime | YES | MUL | CURRENT_TIMESTAMP | | +-------------+--------------+------+-----+-------------------+----------------+ 3 rows in set (0.01 sec)