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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);
25 Αυγ 2009 · If you need to create same PRIMARY KEYs on two tables with identical data, use this: MERGE INTO mytable v USING ( SELECT rowid AS rid, rownum AS rn FROM mytable ORDER BY co1l, col2, col3 ) ON (v.rowid = rid) WHEN MATCHED THEN UPDATE SET pk_col = rn
In this tutorial, you have learned how to use Oracle PRIMARY KEY constraint to create, add, disable, enable, and drop a primary key of a table.
28 Αυγ 2015 · If you want to add a primary key constraint to an existing column all of the previously listed syntax will fail. 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;
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.
