ALTER TABLE是用于修改已有表结构的 SQL 语句。我们可以通过该语句对表的列、约束以及索引进行添加、修改或删除。设置默认值的任务可以通过ALTER COLUMN来完成。基本语法如下: ALTERTABLEtable_nameALTERCOLUMNcolumn_nameSETDEFAULTdefault_value; 1. 2. 其中,table_name是需要修改的表名,column_name是需要设置默认值的...
UPDATE MyTable SET NullCol = N'some_value' WHERE NullCol IS NULL ALTER TABLE MyTable ALTER COLUMN NullCOl NVARCHAR(20) NOT NULL 如果用 CREATE TABLE 或 ALTER TABLE 语句创建或更改表,则数据库或会话设置将影响并且可能覆盖用于列定义的数据类型的为空性。建议您始终将列显式定义为非计算列的 NULL ...
ALTER TABLE modifies a table definition by altering, adding, or dropping columns and constraints. ALTER TABLE also reassigns and rebuilds partitions, or disables and enables constraints and triggers.
SET DEFAULT |SET NULL } ] [ ON UPDATE { CASCADE | NO ACTION | SET DEFAULT |SET NULL } ] } < table_constraint > ::= [ CONSTRAINT constraint_name ] { [ { PRIMARY KEY | UNIQUE } { ( column [ ,...n ] ) } | FOREIGN KEY ( column [ ,...n ] ) REFERENCES ref_table [ (...
s no one-liner version, however, on Enterprise adding a column with a populated default value ...
AlterTableDropTableElementStatement AlterTableFileTableNamespaceStatement AlterTableRebuildStatement AlterTableSetStatement AlterTableStatement AlterTableSwitchStatement AlterTableTriggerModificationStatement AlterTriggerStatement AlterUserStatement AlterViewStatement AlterWorkloadGroupStatement AlterXmlSchemaCollectionStatement ...
如需對應於 SQL 專用權之系統權限的相關資訊,請參閱檢查表格或視圖的專用權時對應的系統權限及檢查特殊類型的專用權時對應的系統權限。 語法 ALTER TABLE表格名稱ADDCOLUMN直欄定義BEFORE直欄名稱ALTERCOLUMN直欄變更DROPCOLUMN直欄名稱CASCADERESTRICTADD唯一限制參照限制核對限制DROPPRIMARY KEYUNIQUEFOREIGN KEYCHECKCONSTRAI...
UPDATE MyTable SET NullCol = N'some_value' WHERE NullCol IS NULL ALTER TABLE MyTable ALTER COLUMN NullCOl NVARCHAR(20) NOT NULL When you create or alter a table with the CREATE TABLE or ALTER TABLE statements, the database and session settings influence and possibly override the nullability...
Alter Table add Column - How do you add a column after say the second column Alter table add constraint primary key clustered identity(1,1) ALTER TABLE ALTER COLUMN (To set the default value) ALTER TABLE Progress? ALTER TABLE SWITCH statement failed. Check constraints or partition function of...
ALTER TABLE — 更改表属性 ALTER TABLE table [ * ] ADD [ COLUMN ] column typeALTER TABLE table [ * ] ALTER [ COLUMN ] column { SET DEFAULT value | DROP DEFAULT }ALTER TABLE table [ * ] RENAME [ COLUMN ] column TO newcolumnALTER TABLE table RENAME TO newtable ...