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- MySQL唯一约束（UNIQUE KEY） - C语言中文网
唯一键（Unique Key）要求该列唯一，允许为空，但只能出现一个空值。唯一约束可以确保一列或者几列不出现重复值。 在创建表时设置唯一键约束 在定义完列之后直接指定唯一约束，语
- Configure incremental models | dbt Developer Hub - dbt Labs
The optional unique_key parameter specifies a field (or combination of fields) that defines the grain of your model That is, the field(s) identify a single unique row You can define unique_key in a configuration block at the top of your model, and it can be a single column name or a list of column names
- Create unique constraints - SQL Server | Microsoft Learn
Applies to: SQL Server 2016 (13 x) and later versions Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric You can create a unique constraint in SQL Server by using SQL Server Management Studio or Transact-SQL to ensure no duplicate values are entered in specific columns that don't participate in a primary key
- sql server - Unique index or unique key? - Stack Overflow
The unique piece is not where the difference lies The index and key are not the same thing, and are not comparable A key is a data column, or several columns, that are forced to be unique with a constraint, either primary key or explicitly defined unique constraint
- What is the difference between a primary key and a unique . . .
Unique Key constraints: Unique key constraint will provide you a constraint like the column values should retain uniqueness It will create non-clustered index by default ; Any number of unique constraints can be added to a table It will allow null value in the column
- MySQL Unique Key - Tpoint Tech - Java
Unique Key Using ALTER TABLE Statement This statement allows us to do the modification into the existing table Sometimes we want to add a unique key to the column of an existing table; then, this statement is used to add the unique key for that column Syntax Following are the syntax of the ALTER TABLE statement to add a unique key:
- SQL - Unique Key, Primary Key Foreign Key - Stack Overflow
A note about Unique key The parent table in a Primary Key-Foreign Key relation is normally called as Primary Key table but PK is not mandatory in a parent table A unique key constraint in parent table is sufficient As PK is always unique, it is often used as foreign key in another table see this SO post
- Defining Unique Constraints in JPA - Baeldung
The unique attribute specifies whether the column is a unique key This is a shortcut for the UniqueConstraint annotation, and is useful when the unique key constraint corresponds to only a single column We’ll see how to define it in the next section 4 2 Defining the Column Constraints
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