修改:添加字段: alter table 表add [column] 字段名 字段类型; 删除字段: alter table 表drop [column] 字段名;修改字段类型: alter table 表modify 字段名 新的字段类型;修改字段名称 : alter table 表change 旧字段名 新字段名 字段类型;修改表名称: alter table 表rename [to] 新表名;查询:...
`name` varchar(200) NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `unique_cluster_name` (`name`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin | # desc TABLE_NAME 获取table中column的信息 desc cluster; +---+---+---+---+---+...
Similarly, if a query uses multiple tables and refers to a column name that is present in more than one table, it's necessary to qualify the name with a table name to make it clear which column you mean. Server startup mode. If the server has been started with the --ansi or --...
mysql> create table t8(id int auto_increment,name varchar(20)); ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key mysql> create table t8(id int primary key auto_increment,name varchar(20)); Query OK, 0 rows affected ...
使用方法: NEW.columnName (columnName 为相应数据表某一列名) 另外,OLD 是只读的,而 NEW 则可以在触发器中使用 SET 赋值,这样不会再次触发触发器,造成循环调用(如每插入一个学生前,都在其学号前加“2013”)。 查看触发器 和查看数据库(show databases;)查看表格(show tables;)一样,查看触发器的语法如下:...
NULL ON EMPTY: The column is set toNULL; this is the default behavior. DEFAULTjson_stringON EMPTY: the providedjson_stringis parsed as JSON, as long as it is valid, and stored instead of the missing value. Column type rules also apply to the default value. ...
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name { LIKE old_tbl_name | (LIKE old_tbl_name) }create_definition:col_name column_definition| [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...)[index_option] ...
The escaping rules for option file values are especially pertinent for Windows path names, which use\as a path name separator. A separator in a Windows path name must be written as\\if it is followed by an escape sequence character. It can be written as\\or\if it is not. Alternatively...
Rebuild the completion hash that enables database, table, and column name completion while you are entering statements. (See the description for the--auto-rehashoption.) resetconnection,\x Reset the connection to clear the session state. This includes clearing any current query attributes defined ...
The following two queries use the same column names, but the context supplied by the FROM clause of each statement indicates the table from which to select the columns: SELECT last_name, first_name FROM president; SELECT last_name, first_name FROM member;...