alter table emp add constraint ppp primary key (id) 2.check约束: 就是给一列的数据进行了限制 比方说,年龄列的数据都要大于20的 表名(emp) 列名(age) 格式: alter table 表名称 add constraint 约束名称 增加的约束类型 (列名) 例子: alter table emp add constraint xxx check(age>20) 3.unique约束...
AddPrimaryKey AddUniqueConstraint AlterColumn AlterDatabase AlterSequence AlterTable CreateIndex CreateSequence CreateTable DeleteData DropCheckConstraint DropColumn DropForeignKey DropIndex DropPrimaryKey DropSchema DropSequence DropTable DropUniqueConstraint ...
ArcGIS Onlineconfirms that existing values in the field are unique.If they are, the unique constraint is added, and theUniquevalue is updated to indicate that the field has a unique constraint applied to it. If values are not unique, you cannot set a unique constraint on this field until ...
我想要往 job 表中 insert 一条数据,报错如题。 原因:要插入 job 表的数据中外键列的值有问题,userId 字段的值在 user 表中找不到。 解决: 确保 job 表中要引用的外键值在 user 表中有对应数据就可以了。 “ you're adding a foreign key, you need to make sure that the data in the child tabl...
This feature is in Public Preview. Applies to: Databricks SQL Databricks Runtime 11.3 LTS and above Defines an informational primary key or informational foreign key constraint for a Delta Lake table. CONSTRAINT name Optionally specifies a name for the constraint. The name must be uniq...
Even if this option isn't set, indexes related to primary keys and UNIQUE constraints are generated if they are already defined on a published table. 0x80 Replicates PRIMARY KEY constraints. Any indexes related to the constraint are also replicated, even if options 0x10 and 0x40 a...
Source: ConstraintCollection.cs 使用指定名称、DataColumn 和指示列是否为主键的值构造一个新 UniqueConstraint,并将其添加到集合中。 C# 复制 public System.Data.Constraint Add (string? name, System.Data.DataColumn column, bool primaryKey); 参数 name String UniqueConstraint 的名称。 column DataColumn ...
CONSTRAINT PK_Person PRIMARY KEY NONCLUSTERED (PersonID, FirstName) ) [/cc]Note: The “CONSTRAINT PK_Name” portion of the code above is optional, however if not specified a constraint name will be auto generated.Prerequisites The primary key column(s) must be unique for each row. If you...
sql ALTER TABLE jylb_loadphaselamps ADD CONSTRAINT pk_line_point PRIMARY KEY (cintsid, xlbh); 如果pk_line_point名称没有被使用,或者你已经成功删除了同名的现有约束,上述语句将成功为jylb_loadphaselamps表添加一个新的主键约束。 如果你选择使用不同的约束名称,只需将pk_line_point替换为你选择的新名称...
unique index 令系统检测当索引创建时（如果数据已经存在）和每次添加数据时表中是否有重复值．如果插入或更新的值回导致重复的记录时将导致一个错误． 而非unique不具备这种功能