SQL Error: Multiple Primary Keys Defined - How to Fix

This error occurs when two or more columns are defined as primary keys in a table. A primary key is a unique identifier for each row in a table, so it cannot have duplicate values. When multiple columns are defined as primary keys, it means that the combination of these columns must be unique for each row.

To fix this error, you need to either remove one of the primary keys or combine them into a composite key. A composite key is a primary key that consists of multiple columns. To create a composite key, you can use the syntax:

CREATE TABLE table_name (
   column1 datatype,
   column2 datatype,
   column3 datatype,
   PRIMARY KEY (column1, column2)
);

This creates a composite primary key with 'column1' and 'column2'.