T-SQL基础之外键约束 首先创建测试表 usetest;createtabletest01 ( id1intnotnull, id2intnotnull);createtabletest02 ( id11intnotnull, id22intnotnull);altertabletest01addconstraintpk_id1primarykey(id1); 考虑如下关系 test02表中的id11依赖于test01中的id1,因此为test02创建外键 altertabletest02addco...
ADD CONSTRAINT DF_Gender DEFAULT (0) FOR Gender; ``` 为`OrderInfo` 表添加外键约束和默认值约束: ```sql ALTER TABLE OrderInfo ADD CONSTRAINT FK_Userld FOREIGN KEY (Userld) REFERENCES UserInfo (Userld), ADD CONSTRAINT FK_Commodity FOREIGN KEY (Commodityld) REFERENCES CommodityInfo (Commodityld)...
---添加外键约束(主表stuInfo和从表stuMarks建立关系,关联字段为stuNo) alter table 从表 add constraint 约束名 foreign key(关联字段) references 主表(关联字段) --sql server中删除约束的语句是: alter table 表名 drop constraint 约束名 --找到数据表中的所有列的约束 sp_helpconstraint 表名 SQL Server ...
添加或者删除一个约束,包括下面这些约束:主键约束(Primary key constraint)、唯一性约束(Unique constraint)、外键约束(Foreign key constraint)、检查约束(Check constraint)、默认约束(Default constraint) 修改表不可以做这些事:修改列名,添加一个特征ID属性(Identity)、删掉一个特征ID属性。 创建和修改表实践: 在这个...
When you create a primary key, SQL Server enforces the constraint behind the scenes by creating a unique index on that column and using the primary key column or columns as the keys of the index. 当你创建一个主键时,SQL Server强制在幕后对这个列创建唯一性索引,并使用主键列作为索引的键。
FeatureFOREIGN KEYApplies to:Azure SQL Database and SQL Server starting SQL Server 2016 (13.x) For memory-optimized tables, FOREIGN KEY constraints are only supported for foreign keys referencing primary keys of other memory-optimized tables. Remove the constraint from the table definition if the ...
AlterSymmetricKeyStatement AlterTableAddTableElementStatement AlterTableAlterColumnOption AlterTableAlterColumnStatement AlterTableAlterIndexStatement AlterTableAlterPartitionStatement AlterTableChangeTrackingModificationStatement AlterTableConstraintModificationStatement ...
AlterSymmetricKeyStatement AlterTableAddTableElementStatement AlterTableAlterColumnOption AlterTableAlterColumnStatement AlterTableAlterIndexStatement AlterTableAlterPartitionStatement AlterTableChangeTrackingModificationStatement AlterTableConstraintModificationStatement ...
Feature FOREIGN KEY Applies to: Azure SQL Database and SQL Server starting SQL Server 2016 (13.x)For memory-optimized tables, FOREIGN KEY constraints are only supported for foreign keys referencing primary keys of other memory-optimized tables. Remove the constraint from the table definition if th...
Feature FOREIGN KEY Applies to: Azure SQL Database and SQL Server starting SQL Server 2016 (13.x)For memory-optimized tables, FOREIGN KEY constraints are only supported for foreign keys referencing primary keys of other memory-optimized tables. Remove the constraint from the table definition if th...