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To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access: CREATE TABLE Persons ( ID int NOT NULL, LastName varchar (255) NOT NULL, FirstName varchar (255), Age int, CONSTRAINT PK_Person PRIMARY KEY (ID,LastName) );
Aug 18, 2011 · You can (and you should) explicitly give a name to your primary key constraint: ALTER TABLE [dbo].[PnrDetails1] ADD CONSTRAINT PK_PnrDetails1 PRIMARY KEY CLUSTERED([OId] ASC) ON [PRIMARY] You can only do this at the time of creation - so in your case, you probably have to drop it first, and then re-create it with the proper, readable name.
May 17, 2024 · ALTER TABLE table_name ADD CONSTRAINT constraint_name PRIMARY KEY (column1, column2, … column_n); SQL PRIMARY KEY Examples. Let’s look at some examples of the PRIMARY KEY Constraint in SQL, and understand it’s working. Create PRIMARY KEY in SQL Example. In this example, we will create primary key in a new table using CREATE TABLE ...
The syntax of the SQL PRIMARY KEY constraint is: CREATE TABLE table_name ( column1 data_type, ..., [CONSTRAINT constraint_name] PRIMARY KEY (column1) ); Here, table_name is the name of the table to be created; column1 is the name of the column where the PRIMARY KEY constraint is to be defined
If the primary key consists of one column, you can use the PRIMARY KEY constraint as a column or table constraint. If the primary key consists of two or more columns, you must use the PRIMARY KEY constraint as the table constraint. Suppose you want to manage the projects and project assignments of the company in the database.
The basic syntax of adding PRIMARY KEY using CREATE TABLE and ALTER TABLE statements and dropping PRIMARY KEY using DROP TABLE statement is given below. CREATE TABLE Syntax. Single column Primary Key. The first CREATE table syntax is without using a constraint name and the second syntax is with a constraint name. Both are valid.
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You create a primary key for a table by using the PRIMARY KEY constraint. If the primary key consists of only one column, you can define use PRIMARY KEY constraint as a column constraint: CREATE TABLE table_name ( pk_column data_type PRIMARY KEY, ... ); Code language: SQL (Structured Query Language) (sql)
