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This tutorial shows you how to use Oracle PRIMARY KEY constraint to create, add, disable, enable, and drop a primary key of a table.
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);
28 Αυγ 2015 · To add a primary key constraint to an existing column use the form: ALTER TABLE `goods` MODIFY COLUMN `id` INT(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT; NOTE: Apparently with some versions of MYSQL you must replace MODIFY with CHANGE (Thanks @csr-nontol !)
An ALTER TABLE statement adding the PRIMARY KEY column works correctly in my testing: ALTER TABLE tbl ADD id INT PRIMARY KEY AUTO_INCREMENT; On a temporary table created for testing purposes, the above statement created the AUTO_INCREMENT id column and inserted auto-increment values for each existing row in the table, starting with 1.
To create a new table with a column defined as the primary key, you can use the keyword PRIMARY KEY at the end of the definition of that column. In our example, we create the table product using a CREATE TABLE clause, with the names of the columns and their respective data types in parentheses.
In this tutorial, you will learn how to use MySQL primary key constraint to create the primary key for a table.
MySQL supports an IGNORE keyword for INSERT, UPDATE, and so forth. If you use it, MySQL ignores primary-key or unique-key violations and continues processing with the next row.
