#access does not allow duplicate values in the primary key field or something?
Access does not allow duplicate values or null values in the primary key field.
Related introduction:
The primary key is one or more fields in the table, and its value is used to uniquely identify a record in the table. In a relationship between two tables, the primary key is used in one table to reference a specific record from the other table. The primary key is a unique key that is part of the table definition. The primary key of a table can be composed of multiple keywords, and the columns of the primary key cannot contain null values. Primary keywords are optional and can be defined in a CREATE TABLE or ALTER TABLE statement.
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