Delete columns using Table DesignerThe following steps explain how to delete columns with Table Designer in SSMS:In Object Explorer, right-click the table from which you want to delete columns and choose Design. Right-click the column you want to delete and choose Delete Column from the short...
It opens a window and lists the column name to remove. Click Ok, and it removes the column from the table. 它打开一个窗口,并列出要删除的列名。 单击确定,它将从表中删除该列。 (SQL DELETE columns using SSMS table designer) We use the table designer in SSMS to define required columns, da...
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alter table [表名] add column [字段名] [类型]; *删除表中的字段: alter table [表名] drop column [字段名]; *重命名一个字段: alter table [表名] rename column [字段名A] to [字段名B]; *给一个字段设置缺省值: alter table [表名] alter column [字段名] set default [新的默认值]; ...
alter table tableName drop column columnName --(其中,tableName为表名,columnName为列名) 但是,如果某列有约束时,不能直接删除,需要先删除约束,再删除列。如果某个列是外键,在不知道外键约束名称的情况下,那么首先是查找外键约束名称,根据名称删除约束,然后再删除列。
DELETE FROM table_name [WHERE condition]; table_name -- the table name which has to be updated.NOTE: The WHERE clause in the sql delete command is optional and it identifies the rows in the column that gets deleted. If you do not include the WHERE clause all the rows in the table ...
DELETEFROM[表名]WHERE[字段名]>100 更新数据: UPDATE[表名]SET [字段1]=200, [字段2]=\'51WINDOWS.NET\'WHERE[字段三]=\'HAIWA\' 新增字段: ALTERTABLE[表名]ADD[字段名]NVARCHAR(50)NULL 删除字段: ALTERTABLE[表名]DROPCOLUMN[字段名]
table_name指的是要修改的表的名字,DROP COLUMN关键字后面为要删除列的名字。一次可以删除多个列,只需要在DROP COLUMN关键字后面依次列出要删除的列的名字,中间用逗号分开即可。实例17 删除BookInfo表中的某列本实例将BookInfo表中新添加的lenddate字段删除,代码如下:...
truncate table 在功能上与不带 WHERE 子句的 delete语句相同:二者均删除表中的全部行。 但truncate 比 delete速度快,且使用的系统和事务日志资源少。 delete 语句每次删除一行,并在事务日志中为所删除的每行记录一项。所以可以对delete操作进行roll back
搜索删除指定搜索条件以限定要删除的行。 例如,WHEREcolumn_name=value。 定位删除使用 CURRENT OF 子句指定游标。 删除操作在游标的当前位置执行。 这比使用 WHEREsearch_condition子句限定待删除行的搜索 DELETE 语句更为精确。 如果搜索条件不唯一标识单行,则搜索 DELETE 语句删除多行。