alter vt. 1.变更;改变,改换;改建(房屋),改做(衣服)。 2.〔美方〕阉割,给(雄性动物)去势,给(雌性动物)割去卵巢。 vi. 变,改;(人)变老。 alter for the better [worse] 改好[坏],变好[坏]。 n. -ability 可变性。 adj. -able 可改变的。 adv. -ably
These alter table statements should be executed with the same care as any insert , update , or delete statement that affects many rows 如同影响许多行的insert 、 update或者delete语句一样,应谨慎执行这些alter table语句。
Columns that do not allow null values can be added with alter table only if they have a default specified or if the table is empty 如果列不允许空值,则只有在指定了默认值或表为空的情况下,才能用alter table语句添加该列。
Use session user with default constraints in either the create table or alter table statements , or use it as any standard function Session _ user可在create table或alter table语句中与default约束一起使用,或者将它用作任何标准函数。
Scripts that do not enforce triggers and constraint checks to fail if the user account lacks alter table permissions for the target table 如果用户帐户没有对目标表的alter table权限,这项新要求有可能导致不强制使用触发器和约束检查的
Columns created without an explicit null or not null option in create table or alter table are created as not null . the nullability of 列时,如果在create table或alter table中没有显式地指定null或not null选项,则该列将按not null创建。
If there are any execution plans in the procedure cache that reference the table , alter table marks them to be recompiled on their next execution 如果过程缓存中存在引用表的执行计划, alter table会将这些执行计划标记为下次执行时重新编译。
Type column from untyped to typed xml , or vice versa , by using the alter table alter column option , no xml index on the column should exist 类型列从非类型化的xml更改为类型化的xml ,或者从类型化的xml更改为非类型化的xml ,则列不应存在xml索引。
This setting only affects the nullability of new columns when the nullability of the column is not specified in the create table and alter table statements 仅当create table和alter table语句中没有指定列的为空性,此设置才能影响新列的为空性。
For example , execute alter table drop column at the publisher , and the statement is replicated to subscribers and then executed to drop the column 例如,在发布服务器上执行alter table . . . drop column ,该语句将复制到订阅服务器,然后执行以删除列。
If the alter table statement requires changing a column used in a schema - bound view , alter table fails and the database engine raises an error message 如果alter table语句要求更改用于架构绑定视图中的列, alter table将失败,并且数据库引擎将引发错误消息。