Αποτελέσματα Αναζήτησης
This tutorial shows you how to use Oracle PRIMARY KEY constraint to create, add, disable, enable, and drop a primary key of a table.
The syntax to create a primary key using the ALTER TABLE statement in Oracle/PLSQL is: ALTER TABLE table_name ADD CONSTRAINT constraint_name PRIMARY KEY (column1, column2, ... column_n); Example. Let's look at an example of how to create a primary key using the ALTER TABLE statement in Oracle.
To create a PRIMARY KEY constraint on the "ID" column when the table is already created, use the following SQL: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Persons. ADD PRIMARY KEY (ID);
Oracle PRIMARY KEY Constraint with Examples. In this article, we will be learning about the Primary constraints and how to create, alter, drop or enable/disable them in Oracle. What is a Primary Key? The Primary Key constraint is used for uniquely identifying each row of a table.
28 Αυγ 2024 · This article will explain the fundamentals of primary keys with examples of creating, altering, dropping, enabling, as well as disabling primary key constraints using PL/SQL.
8 Μαΐ 2017 · But as you want a primary key anyway, you can drop the separate not-null check, as it's implied by a (proper) primary key: ALTER TABLE buses MODIFY Bus_no NULL; ALTER TABLE buses ADD CONSTRAINT PK_BUSES PRIMARY KEY (Bus_no); desc buses.
For example: create table DEPARTMENTS ( . deptno number, . name varchar2(50) not null, . location varchar2(50), . constraint pk_departments primary key (deptno) . ); Tables can declarative specify relationships between tables, typically referred to as referential integrity.
