add primary key to the table code example
Example 1: add primary key to existing table sql
alter table Persion add primary key (persionId,Pname,PMID)
Example 2: sql primary key
A primary key allows each record in a table to be uniquely identified. There can only be one
primary key per table, and you can assign this constraint to any single or combination of columns.
However, this means each value within this column(s) must be unique.
Typically in a table, the primary key is an ID column, and is usually paired with the AUTO_
INCREMENT keyword. This means the value increases automatically as new records are created.
CREATE TABLE users (
id int NOT NULL AUTO_INCREMENT,
first_name varchar(255),
last_name varchar(255) NOT NULL,
address varchar(255),
email varchar(255),
PRIMARY KEY (id)
);
Example 3: add primary key to existing table sql
ALTER TABLE `tblauto`
ADD PRIMARY KEY (`id`);
Example 4: what is primary key
PRIMARY KEY