Can a table have only one primary key or not?

Limitations and Restrictions A table can contain only one PRIMARY KEY constraint. All columns defined within a PRIMARY KEY constraint must be defined as NOT NULL. If nullability is not specified, all columns participating in a PRIMARY KEY constraint have their nullability set to NOT NULL.
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Can a table have only one primary key?

A primary key is a field or set of fields with values that are unique throughout a table. Values of the key can be used to refer to entire records, because each record has a different value for the key. Each table can only have one primary key.
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Can a table have only one primary key but multiple foreign keys?

A primary key uniquely identifies a row In the table. A foreign key references the primary (or in some systems any unique key) in another table thereby establishing a relationship between the two tables. A table may have only one primary key, but may have zero to many other unique keys.
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Does each table need a primary key?

It's very important that a table has a Primary Key. There are two good reasons why a table should have a Primary Key. First, a Primary Key uniquely identifies each record in a table so it helps to ensure against redundant data in that table. This also means that we can "point" to a specific record in the table.
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Can a table contain no primary key?

The short answer is YES. A database table can exist without a primary key. But without having a primary key on a table you are leaving the door open for potential data management/inconsistency headaches.
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Why only one primary key for a Table?

How many primary keys are in a table?

The PRIMARY KEY constraint specifies that the constrained columns' values must uniquely identify each row. A table can only have one primary key, but it can have multiple unique constraints.
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Can a table have only a foreign key and no primary key?

A foreign key is one or more columns in a table that references the primary key of another, creating a link between them. Foreign keys cannot exist without being linked to a primary key. Unlike primary keys, tables can have more than one foreign key.
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Should a table have multiple primary keys?

The short answer is no, a table is not allowed to contain multiple primary keys , as that goes against the fundamental principles of relational database design (see: [database normalisation](https://en.wikipedia.org/wiki/Database_normalisation) and [Third normal form](https://en.wikipedia.org/wiki/Third_normal_form) ).
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Can two tables have the same primary key?

Yes two table can have the same primary key.
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Can primary key be NULL?

The primary key is the minimum set of traits that distinguishes any row of a table. It cannot have NULL and duplicate values. The primary key is used to add integrity to the table. In the case of a primary key, both Duplicate and NULL values are not valid.
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Are primary keys unique?

The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values.
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Can one primary key have two foreign keys?

The answer is Yes. The foreign key, as we know, is the attribute constraint that helps define the relationship between two tables. A single table can be related to more than one table in the database. It can thus have more than one foreign key.
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Can we have primary key and foreign key in same table?

Yes. It is possible. Example: an employee table with emp_id as primary key might also include a manager column as foreign key to the emp_id of the same table.
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Can a foreign key be a primary key?

Foreign keys are almost always “Allow Duplicates,” which would make them unsuitable as Primary Keys. It is perfectly fine to use a foreign key as the primary key if the table is connected by a one-to-one relationship, not a one-to-many relationship.
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Can a foreign key be NULL?

A table can have many foreign keys. A foreign key is nullable if any part is nullable. A foreign key value is null if any part is null.
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Should a table have a primary key True or false?

A primary key is the column or columns that hold values that uniquely recognize each row in a database table. A database table must have a primary key for Optima to insert, update, restore, or delete data from a database table. A database table can have only one primary key, which can have single or multiple columns.
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Why is there only one primary key in a table?

The data in a specific column is always unique. A database table can only have one primary key. It uniquely identifies a record in a relational database table. The value of a primary key can't be deleted from the tree structure or the parent table.
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Can a table have one primary key and many unique key?

A table can't have more then one primary key because If we create multiple primary key then it will be unable to detect the unique key value. Every table can have only one primary key. primary key needs to be unique, can't be null and it does not accepts duplicate value.
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Can a table have duplicate primary keys?

You can define keys which allow duplicate values. However, do not allow duplicates on primary keys as the value of a record's primary key must be unique. When you use duplicate keys, be aware that there is a limit on the number of times you can specify the same value for an individual key.
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How many primary keys does a table have?

You can have only one primary key for a table.
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Should each table have a primary key?

Each table must have exactly one primary key: a subset of its attributes that uniquely identify each entity in the table. The database uses the primary key to prevent duplicate entries, to relate data across tables, and to accelerate data queries. The choice of the primary key will determine how you identify entities.
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Can a table have no primary key?

The data columns in your table might not need a primary key. To replicate tables that do not have primary keys, you can specify a unique index or add the ERKEY shadow columns. You can specify an existing unique index or unique constraint as the replication key when you define the replicate.
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Can a table have multiple foreign keys and no primary key?

Yes, a single table can have multiple foreign keys. Each foreign key in a table establishes a relationship with a primary key in another table (or potentially the same table, in the case of self-referencing relationships).
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Can two tables have the same primary key and foreign key?

Answer: Yes, a primary key from one table can act as a foreign key in two different tables. It is a common scenario in database design for maintaining referential integrity and establishing relationships between tables.
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Can there be only one foreign key in a table?

Foreign keys

These link two tables together. It is possible to have more than one foreign key in a table, and they can accept a null value. Foreign key values do not need to be unique; duplicate values can be stored in foreign key columns. Foreign keys do have to link back to columns with unique values.
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