This Oracle tutorial explains how to create, change, drop, disable, and enable a primary key in Oracle with syntax and examples. In Oracle, a primary key is a single field or combination of fields that uniquely defines a record.
While SQL Server only allows one PRIMARY KEY constraint assigned to a single table, that PRIMARY KEY can be defined for more than one column. In a multi-column scenario, individual columns can contain duplicate, non-unique values, but the PRIMARY KEY constraint ensures that every combination of...
1.禁用该约束 select*fromuser_constraints cwherec.table_name='TABLE_NAME'; alter table TABLE_NAME disable constraint CONSTRAINT_NAME CASCADE; 2.删除表的时候,级联删除约束 drop table TABLE_NAME cascade constraints;
public interface PrimaryKey extends RowPrimaryKey is a specialization of Row to represent a primary key used to access records in a table using the TableAPI. It may contain all or part of a primary key for its associated table. If an attempt is made to set a field that is not part of...
rare cases, the standard incremental nature built into theSERIALandBIGSERIALdata types may not suit your needs. In these cases, you can perform the same auto incremented primary key functionality for your column by creating a customSEQUENCE, similar to the method used in older version of Oracle...
PRIMARY KEY(E_Id) ) Mysql/SQl Server/Oracle/MS Access: CREATE TABLEEmployee ( E_IdintNOT NULL, LastNamevarchar(255)NOT NULL, FirstNamevarchar(255), Addressvarchar(255), Cityvarchar(255), CONSTRAINT ak_EmployeeID PRIMARY KEY(E_Id,LastName) ...
如果在表已存在的情况下为 "ID" 列创建 PRIMARY KEY 约束,请使用下面的 SQL:MySQL / SQL Server / Oracle / MS Access:ALTER TABLE Persons ADD PRIMARY KEY (ID); 要允许主键约束的命名,并在多列上定义主键约束,请使用以下SQL语法:MySQL / SQL Server / Oracle / MS Access:ALTER TABLE Persons ADD CON...
Oracle PL/SQL:CREATE TABLE statement: create a table with primary key.CREATE TABLE statement can be used to create table objects in database. It is possible to add constraints like primary key ,foreign key while table creation.Primary key is the unique identifier for a row of data.One ...
MySQL / SQL Server / Oracle / MS Access: ALTER TABLE PersonsADD PRIMARY KEY (Id_P) 如果需要命名 PRIMARY KEY 约束,以及为多个列定义 PRIMARY KEY 约束,请使用下面的 SQL 语法: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE PersonsADD CONSTRAINT pk_PersonID PRIMARY KEY (Id_P,LastName...
id INT PRIMARY KEY, column1 VARCHAR(50) ); -- Unique Key CREATE TABLE example_table ( id INT UNIQUE, column1 VARCHAR(50) ); Auto-increment Primary Key in SQL: Description:An Auto-increment Primary Key is a numeric value that automatically increments. Commonly used for surrogate keys. ...