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A field that is not unique and null can not be used as a primary key. Praimary key must satisfy the conditions of not null and unique.
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What is an unlikely primary key?
A first name, a surname, a date of birth, and an address are just some examples of fields that would not be used as primary keys. Lots of people will have the same name or same date of birth and you could have people in your database that are living at the same address, so they are likely to be duplicated and so none of those fields should be used as primary key fields.
Is non key is same as those key that are not primary key?
A non-key field can be any field in the table that is not the primary key. During the process of normalisation identifying non-key fields is important, as they and other fields may be moved and new tables created. Foreign keys will be left in the table.
What is added to a relational database to eliminate many to many relationships?
A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.A junction table is added between the two tables involved in the relationship. The primary key from each table is added to the junction table and they are made a joint primary key in that table. Then two one-to-many relationships are set up between the junction table and each of the two other tables.
Short answer questions will most likely test you on?
key concepts.
A condition in which one attribute is dependent on another attribute when neither attribute is part of the primary key?
transitive dependency
Which field MS Access will not allow you to delete?
A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.A primary key field.
Can the FirstName column be a primary key?
Yes, the FirstName column can be a primary key as long as it satisfies the requirements of a primary key, which include being unique and not null. However, it is generally not recommended to use a person's first name as a primary key as it may not be unique and could lead to data integrity issues.
Is the last name a primary key?
In some cases, a last name can be used as a primary key if it uniquely identifies each record in a dataset. However, it is generally not recommended to use a last name as a primary key due to the potential for duplication or changes over time. It is often better to use a combination of attributes to create a more robust primary key.
Can super key be as primary key?
I think super key is treated as the primary key because in a table their will be only one primary key.
Is a student id number a likely primary key?
Yes, because it is probably unique to each student.
What are the importance of primary key?
Importance of primary key
What does the primary key in a data base do?
We know that primary key is the one that is not null and is always unique. A primary key uniquely identifies a record in a table.
What are the advantage of primary key?
Primary key that is used to identify a record uniquely. Primary key is a key that always unique and not null. A system generated primary key is called surrogate key.Primary key is the one which is always unique and not null. Advantage of primary key that it helps in identifying a tuple uniquely.
What is the primary key for the properties table?
Primary key is to set property ID as the primary key for the properties table.
How you create or assign primary key?
A primary key is never null and is also unique . Example of primary key is create table emp (ecode integer NOT NULL PRIMARY KEY);
When would you use a Primary Key and when would you not?
A primary key is a key that is unique. A primary key is used to identify a record uniquely. There is not any particular case to not have a primary key . If you want to identify your records you should have a primary key or a surrogate key(as an alternative to it) .In reality, you should always have a primary key. A primary key is there to uniquely identify each record, as it is like other elements would be duplicated. If you had a very large amount of names of people, then it is highly likely that the same firstname or same surname or even the same full name will come up more than once. Having a primary key distinguishes them as each primary key has to be unique.Situations where you might not use it is where you have a very defined set of values where there is guaranteed to be no duplicates, like a database that has the 12 months of the year or a list of regions that all have different names. You still could make them primary keys, but in the case of the months, it would change them into alphabetical order, which you would not want, so that would be another reason for not using a primary key. To keep them in order, you could add another field, with the values from 1 to 12 and use that field as the primary key.
Why do you designate one of the candidate key of relation to be the primary key?
We designate one of the candidate key of a relation to be a primary key because that primary key is use for any foreign key references.
