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To create a PRIMARY KEY constraint on the "ID" column when the table is already created, use the following SQL: ALTER TABLE Persons. ADD PRIMARY KEY (ID); To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax: ALTER TABLE Persons.
In this tutorial, you will learn how to use MySQL primary key constraint to create the primary key for a table.
28 sie 2015 · If we want to make our table to have primary key set {old_key, new_key}, then the following statement can be used: ALTER TABLE my_test_table DROP PRIMARY KEY, -- You have to add this ADD PRIMARY KEY( old_key, -- Re-mention the old key new_key -- And mention also the new one );
To add a primary key for a new MySQL table, use the CREATE TABLE statement, replacing the placeholder values with your own: CREATETABLEyour_table_name(column1<column_definition>,column2<column_definition>,...PRIMARYKEY(customer_id,LastName));
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.
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.
You can create a primary key in MySQL with the ALTER TABLE statement. Syntax. The syntax to create a primary key using the ALTER TABLE statement in MySQL is: ALTER TABLE table_name ADD CONSTRAINT [ constraint_name ] PRIMARY KEY [ USING BTREE | HASH ] (column1, column2, ... column_n)
