SQL Server 2016(13.x)及更高版本 Azure SQL 数据库 azure SQL 托管实例 Microsoft Fabric中的 SQL 数据库 主键和外键是两种类型的约束,可用于强制 SQL Server 表中的数据完整性。 这些是重要的数据库对象。 主键约束 表通常具有包含唯一标识表中每一行的值的一列或一组列。 这样的一列或多列称为表的主键 ...
Creating a Primary Key in SQL Using Code Adding a Primary Key to an Existing Table Types of Primary Keys Understanding the Properties and Rules of an SQL Primary Key Uniqueness and Non-Nullability Limitations and Considerations Benefits of Using Primary Key Constraints Further Learning Understanding ...
Here, the SQL command creates two foreign keys (buyerandseller) in theTransactionstable. Note:As with other constraints, naming aFOREIGN KEYconstraint usingCONSTRAINT constraint_nameis optional. But doing so makes it easier to make changes to or delete the constraint. This is especially helpful wh...
These constraints are: SQL NOT NULL UNIQUE PRIMARY KEY FOREIGN KEY CHECK DEFAULT In this article, we will go through the first three constraints; SQL NOT NULL, UNIQUE and SQL PRIMARY KEY, and we will complete the rest three constraints in the next article. Let us start discussing...
SQL Server / Oracle / MS Access: CREATETABLEOrders ( OrderID intNOTNULLPRIMARYKEY, OrderNumber intNOTNULL, PersonID intFOREIGNKEYREFERENCESPersons(PersonID) ); To allow naming of aFOREIGN KEYconstraint, and for defining aFOREIGN KEYconstraint on multiple columns, use the following SQL syntax: ...
Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) Warehouse in Microsoft Fabric SQL database in Microsoft Fabric Contains a row for each object that is a primary key or unique constraint. Includessys.objects.typePK and UQ. ...
Learn about SQL Foreign Key constraints, their importance in database management, and how to implement them effectively in your SQL databases.
create table user( id int(10) primary key, name varchar(32) ); # 给主键重命名 # table_constraints 专门用来存储字段约束信息 create table user_id( id int(10), name varchar(32), constraint user_id_pk primary key(id) # 原来主键是id现在主键变成 user_id_pk ); 示例 mysql> desc user...
SQL Server 2016 (13.x) and later versions Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric Primary keys and foreign keys are two types of constraints that can be used to enforce data integrity in SQL Server tables. These are important database objects. ...
SQL Server 2016 (13.x) and later versions Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric Primary keys and foreign keys are two types of constraints that can be used to enforce data integrity in SQL Server tables. These are important database objects. ...