how to declare a primary key in sql code example
Example 1: how to define a composite primary key in sql
CREATE TABLE person(id INT,
name TEXT,
PRIMARY KEY (id, name)
);
Example 2: primary key sql
A primary key is a field in a table which uniquely identifies each row/record in a database table. Primary keys must contain unique values. A primary key column cannot have NULL values.
A table can have only one primary key, which may consist of single or multiple fields. When multiple fields are used as a primary key, they are called a composite key.
If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s).
Example 3: primary key in sql
PRIMARY KEY