column1, column2, ... column_n The columns that make up the unique constraint. Example Let's look at an example of how to add a unique constraint to an existing table in SQL Server using the ALTER TABLE statemen
自SQL Server 2016 (13.x) 起,可以对列存储索引创建一个或多个非聚集行存储索引,并对基础列存储执行高效表查找。 其他选项也可供使用。 例如,可以通过在行存储表中使用 UNIQUE 约束来强制主键约束。 由于非唯一值无法插入到行存储表中,因此 SQL Server 无法将值插入列存储。
There's no guarantee that hierarchyid values in a column are unique unless the application uses a unique key constraint or enforces uniqueness itself through its own logic. Hierarchical relationships represented by hierarchyid values aren't enforced like a foreign key relationship. It's possible, ...
Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Specifies the properties of a PRIMARY KEY, FOREIGN KEY, UNIQUE, or CHECK constraint that is part of a new column definition added to a table by using ALTER TABLE. Napomena For Microsoft Fabric, visit ALTER TABLE column_...
When a UNIQUE constraint is added to an existing column or columns in the table, by default, the Database Engine examines the existing data in the columns to make sure all values are unique. If a UNIQUE constraint is added to a column that has duplicate values, the Database Engine ...
lightDao.loadByIds(StaffInfoVO.class,"S2007") //唯一性验证 lightDao.isUnique(staffInfo, "staffCode"); 2.2 支持代码中对象查询 sqltoy 中统一的规则是代码中可以直接传sql也可以是对应xml文件中的sqlId /** * @todo 通过对象传参数,简化paramName[],paramValue[] 模式传参 * @param <T> * @...
_DATA_SOURCE='data_source_name'] [ ,FIRSTROW=first_row] [ ,LASTROW=last_row] [ ,MAXERRORS=maximum_errors] [ ,ERRORFILE='file_name'] [ ,ERRORFILE_DATA_SOURCE='data_source_name'] [ ,ROWS_PER_BATCH=rows_per_batch] [ ,ORDER( { column [ASC|DESC] } [ , ...n ] ) [UNIQUE] ...
When aUNIQUEconstraint is added to an existing column or columns in the table, by default, the Database Engine examines the existing data in the columns to make sure all values are unique. If aUNIQUEconstraint is added to a column that has duplicate values, the Database Engine returns an ...
有关详细信息和使用 BULK INSERT 的安全注意事项,请参阅使用 BULK INSERT 或 OPENROWSET(BULK...) 导入批量数据 (SQL Server)。 从Azure Blob 存储导入数据且数据非公共数据(匿名访问)时,请基于使用MASTER KEY加密的 SAS 密钥创建一个DATABASE SCOPED CREDENTIAL,然后创建一个外部数据库源以用于 BULK INSERT 命令...
Schemas allow you to group related objects together as well as provide a security container for objects. The most important decision you can make when designing a table is the data type of a column. You can use a column set defi nition along with sparse columns to create ta...