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Related 6. Hot Network Questions. As we know primary key column of a table is always unique so we can use that column value to auto generate employee code. I made the 'EmpCode' column a computed column and specified the formula to generate the auto incremented alphanumeric number.
Skip navigation Sign in. If you add a primary key to a table that already has data. The data in the column s , which will be included in the primary key, must be unique and not NULL. You use the KEY when you want to create an index for a column or a set of columns that is not the part of a primary key or unique key.
Suppose that email and username of users in the users table must be unique. In this tutorial, you have learned how to create a primary key for a new table or add a primary key to an existing table.
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