Candidate keys in database

Since AB consists of 2 attributes (A and B), therefore it can be referred to as a composite key. Natural keys and surrogate keys are the two categories of keys. There can be multiple Candidate Keys in one table. Prime attributes are the attributes of the candidate key which defines the uniqueness (Eg: SSN number in an employee database) A primary key is a column in a table whose values uniquely identify the rows in the table. ส่วน Super Key อื่น ๆ ถือว่าผิดเงื่อนไขที่สอง คือ มี Unique Subset เกิดขึ้น. If that reduced set of columns is still a key (i. There can be multiple SQL candidate keys in a database relation and each candidate can work as a primary key for the table. 3 candidate keys for R are AB, BC, and BD. A CK (candidate key) is a superkey (unique column set) that doesn't contain a smaller one. Based on the drawing, we can tell that we need album_name, artist_name and song_name to get all attributes. It means that no two records can have the same value for the candidate’s key attributes. In this paper, a simple straightforward method to find all the candidate keys of a relational database schemes using graph is presented. A candidate key defined as it is a single key or a group of multiple keys that uniquely identify rows in a table. However, the goal of the E-R diagram is to create a simplified “bird’s eye” view of your data. A table can have multiple candidate keys, and each candidate key can qualify as a primary key. suppose if ABC is a candidate key then neither A, B, C or any of its combination can be super key, hence we can say candidate key is a minimal set of attributes of an R ( Relational Schema) which can be used to identify a tuple of a table uniquely. Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Your role as an analyst/designer is to validate such properties, and to fit them into a normalized database model Mar 15, 2024 · Here are a few key reasons why candidate keys are important in the field of database design: Onlyness: Candidate keys ensure that each tuple within a relation can be only identified, preventing duplicate or conflicting data entries. Key attributes can never be NULL. In conclusion, the distinction between a primary key and any other candidate key is artificial and retained because of the early history of relational databases. 7. Unique key 1. Compound Key. g. Each Candidate Key can qualify as Primary Key. Sep 26, 2022 · It can be a natural key, surrogate key, or a composite key. A candidate key is a combination of attributes that uniquely identify a database record without referring to any other data. In this article, we will discuss the candidate key in SQL and how they are used to maintain the integrity and consistency of a database. In other words candidate keys are minimal super keys. Therefore, the candidate key of our table is: {album_name, artist_name, song_name} Oct 22, 2009 · The debate instigated an in-depth discussion about candidate keys and primary keys. Candidate Key A selected group of the candidate keys in a database is called a super key. Let’s look at each of the keys in DBMS with example: Super Key – A super key is a group of single or multiple keys which identifies rows in a table. A material, or a collection of many attributes, makes up the Super Key. Means in Super Key (BookId, BookName) record can be uniquely identify by just BookId and therefore BookName is redundant attribute. DBMS keys are used to specify identifying attributes in the rows of Jun 7, 2023 · Summary. Each table may have one or more candidate. Candidate keys are defined as a distinct set of attributes from which the primary key can be selected. Concept of Keys in DBMS - Super, Primary, Candidate, Foreign Key, simple, composite, and alternate keyشرح الانواع المفاتيح في قاعدة البيانات ومنها Candidate databases are tools to store a candidate’s information, like contact details, CV, notes, etc. Super Keys: Super key stands for superset of a key. . A candidate key is also known as a “unique identifier” or “primary key. Primary key 2. Calculates A candidate key, on the other hand, is not automatically indexed, so the database may need to do a more expensive scan of the table to find rows that match a given candidate key. Importance in Database Design. The value of candidate key must always be unique. In a “Students” table, we can have the following candidate keys: Jun 26, 2019 · Contoh Kasus. I've read through What is the difference between 3NF and BCNF? and can understand the difference between 3NF and BCNF when referring to non-arbituary words within a database Aug 6, 2017 · 6. Without any context, it would be hard to guess what people are talking about when they talk about candidate keys. Most database authors provide a definition for the key, but no algorithm for Jul 12, 2022 · Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. Feb 15, 2023 · A candidate key is a minimal super key in a relational database table. answered Jan 10, 2018 at 14:13. Primary key is the Candidate key selected by the database administrator to uniquely identify tuples in a table. They are considered candidate keys since they can uniquely identify Oct 4, 2009 · What are Candidate Keys? A candidate key is any column or a combination of columns that can qualify as a unique key in the database. A candidate key is typically a set of one or more fields that, together, uniquely identify a record in a table. An example of Primary key and Candidate key can be ID and SSN number in an Employee table, Since both can identify each employee uniquely they are candidate key Feb 24, 2016 · We know that the closure of ABD, ADE, ADF, BED, etc. It is possible to have multiple candidate keys. So we sometimes say a CK is a "minimal" superkey, using "minimal" in this sense of a particular superkey not being able to be made into smaller superkey by removing attributes. One of these candidate keys is selected as the table primary key. Relational keys Apr 17, 2024 · A composite key is a candidate key consisting of two or more attributes (table columns) that uniquely identify a record/tuple (table row) or a relation. phone number isn't unique), the shortest superkey is StudentNumber. Understand how to use each type of key effectively with detailed examples to design robust and efficient database schemas. Foreign Key. The value for the CK is unique and non-null for all tuples. Third , a primary key is a mandatory constraint, which means that every row in the table must have a non-null, unique value in the primary key column. But before proceeding to this topic, we will first learn about what is functional dependency. A candidate key is simply the "shortest" superkey. which can define every tupple in the relation (table) uniquely. It is the theoretical foundation for technical concepts like primary and alternate (unique) keys. A candidate key appears in each candidate key table with exactly one non-null item. Difference between Candidate Key vs Primary Key:- ) Both Primary and Candidate keys can uniquely identify records in a table on database. A more generalized algorithm is provided which allows a uniform and simplified solution to find all possible keys of a relational database schema when the attribute graph of Functional Dependencies (FDs) is not strongly connected. song_name -> song_duration. A set of minimal attribute (s) that can identify each tuple uniquely in the given relation is called as a candidate key. Remove the attributes of the RHS of these from your superkey. Database keys are essential components of a relational database management system. a primary key is a candidate key chosen as the smallest number of unique attributes. COMPUTING THE CANDIDATE KEYS OFR A universal relation is a relation which includes all attributes of the database. The value of candidate key can never be NULL. Candidate Key; A candidate key is a set of one or multiple columns in a database table. Candidate Key Oct 10, 2012 · Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. A candidate key in SQL can have a variety of qualities, but it must not include null values and must have at least the bare minimum of fields to Oct 31, 2016 · a. Second normal form ( 2NF ), in database normalization, is a normal form that is met if each attribute that is not part of the primary key depends on all parts of the primary key. would form the keys. a. So your overlapping candidate keys are NM and NO (they share N). Diketahui table seperti pada dibawah ini, dan kita akan mencoba untuk menentukan yang mana yang super key, candidate key, dan primary key. It must have distinct values. First Name, Last Name, Date of Birth. These keys are all candidate keys, as they are an option or candidate to be the primary key. Candidate keys: Choosing the right primary key. This key is a subset of Super keys and is devoid of any unnecessary attributes, it is not important for uniquely identifying tuples. Candidate key 3. Primary Key- A primary key is a candidate key that the database designer selects while designing the Mark candidate keys in your table structures by writing the letters "CK" next to the name of each field you designate as a candidate key. Mari kita lihat beberapa contoh candidate key database yang umum digunakan dalam desain basis data. Whether or not to allow nullable columns in a key is implementation dependent. Dec 11, 2018 · The candidate keys we have selected are: {Emp_Id} {Emp_Number} Note: A primary key is selected from the set of candidate keys. Here's a guide to primary, super, foreign and candidate keys, what they're used for in relational database management systems and the differences among them. Doing so gives you two keys, that are certainly superkeys, but not necessarily irreducible ones: ABDEF and ABDFG. R is in 3NF, but not in BCNF. On an attribute or set of attribute that is able to form primary key of the table, rest of that remains in the candidate key which is known as alternate key of the Sep 22, 2023 · In a database, keys are used to create relationships between tables, making it possible to easily link and retrieve data. Mar 4, 2024 · The candidate key in DBMS plays a pivotal role in database management systems by serving as a unique identifier for records within a table. One of the fundamental concepts in DBMS is the use of various types of keys – Super, Candidate, Primary, and Foreign Keys. The main purpose of a candidate key is to identify a unique identifier for a Basically, candidate keys are a sub-set of Super keys. It is also used to ensure data integrity by preventing duplicate entries in the database. ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName); Note: If you use the ALTER TABLE statement to add a primary key, the primary key column (s Aug 10, 2021 · Now, 2 possible candidate keys here would be AB and BC. Primary key: No_fak. The various keys in MySQL are: Primary Key; Unique There are two. it is depending on the types of the DBMS Keys used) from any table in the Database system that brings about to distinctively categorize a row Second normal form. Natural Key: A column, or group of columns, that is generated from the table's data is known as a natural key. For instance, since it uniquely identifies every Apr 3, 2022 · Both constraints may be referenced by a foreign key definition. When there are multiple possible keys in a table, these keys are referred to as candidate keys. edited Dec 1, 2011 at 9:55. Composite key 7. One of the candidate keys is designated to be the official primary key (PK). Hence we can also remove the E from our ABDEF key. Apr 15, 2021 · The candidate key, also simply called a key, is an important part of database design. We present new algorithms to compute candidate keys and third normal form design of a relational database schema, using strategic port graph rewriting. Example: You could use name or id as a minimal key. 5. Select any of the as Primary Key for your table, since a table can have only a single Primary Key. Alternate key 6. edu We provide an efficient algorithm for computing the candidate keys of a relational database schema. When selecting Primary keys in DBMS or an alternate key, it’s vital to consider all the following criteria for valid keys. Candidate key means exactly the same thing as primary key. He states that a minimal key is the fewest number of attributes so he means a primary key when he says minimal 2. First you have to understand that all the candidate keys are super keys. The candidate key also helps in determining prime and non-prime attributes. The solution resolves. A table contains only one primary key, but it can contain Jan 12, 2023 · In the field of database management systems (DBMS), a candidate key is a set of one or more columns that can uniquely identify a row within a table. ”. For Example: In the Employee table, Employee_PhoneNumber will have unique values thus it can be used as an alternate key but it is not a primary key. The primary key is a candidate key that is selected by the database designer to be used as an identifying mechanism for the whole entity set. It is up to the database designer who chooses the primary key from the given set of candidate key . The DBMS keys or the Database Management System Keys represent one or more attributes (i. Jul 20, 2014 · These two keys can be candidate keys, as remaining keys are having redundant attributes. Additional explanation of the above, originally left in comments: All overlapping candidate keys are groups of (e. But all candidate keys are super keys. " In this article, we will discuss the importance of candidate keys in DBMS and how they are used to maintain the integrity A candidate key is a set of one or more attributes that can uniquely identify each record within a table in a relational database. Primary Key – is a column or group of columns in a table that uniquely identify every row in that table. Lets talk about those keys one by one. Contoh 1: Tabel “Pengguna” Misalkan kita memiliki tabel “Pengguna” yang berisi informasi tentang pengguna di sebuah sistem. Calculates the closure of each element in the power set of given attributes. A Super Key is a set of one or more attributes that are taken collectively and can identify all other attributes uniquely. For example, a candidate key can be a combination of the candidate’s name and email address, which would be unique to each candidate. The next step is to illustrate these dependencies with a drawing. Attribute closure calculator, Candidate key calculator, Minimum (Canonical) cover calculator, Functional dependency calculator and Normal form calculator. There exists no general formula to find the total number of candidate keys of a given relation. A functional dependency X->Y in a relation holds if two tuples having the same value Jul 15, 2020 · Primary Key in SQL. Jenis key dalam database selanjutnya adalah Candidate key ini berperan sebagai untuk mengidentifikasi adanya kejadian yang spesial pada tabel anda. This means that a candidate key is a set of one or more attributes (columns) that uniquely identifies a tuple (row) in a table, and it has the least number of attributes needed to do so. Let us first try to grasp the definition of the two keys. Jun 20, 2020 · Database candidate keys sometimes become primary keys. All Candidate keys are Super keys. These keys are a critical part of the database design process as they help ensure data integrity and accuracy. Oct 1, 2023 · Oct 1, 2023. Choosing the right candidate key for a database is essential to ensure data integrity and accuracy. There can be multiple Oct 28, 2014 · Overlapping candidate keys are composite (consist of more than one attribute) candidate keys with at least one attribute in common. two or more) candidate keys. More formally, a relation is in the second normal form if it fulfills the following two requirements: Sep 19, 2023 · 1. pada candidate key ini juga memiliki syarat sebuah kunci yang dinamakan candidate key adalah unik The primary key index is automatically created when the primary key is defined, whereas the candidate key index needs to be explicitly created. Jun 15, 2020 · Example. To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Persons. Foreign key 5. Jun 27, 2022 · DBMS keys: 8 types of keys defined. Candidate Keys: Candidate Keys are super keys for which no proper subset is a super key. If none of the candidate keys is simple and intelligible, an artificial key, often called the identifier, is created. But can we have two candidate keys in a relation different in length? Yes. We provide an efficient algorithm for computing the candidate keys of a relational database schema. 2) Both Primary and Candidate keys are has constraints UNIQUE and NOT NULL. All super keys can’t be candidate keys. A table may contain one or more candidates and one of those candidate keys has to be referred to as the primary key. For each k in K do: Remove all the keys sk in K such that k is a Jun 5, 2024 · A candidate key is a term used in database management that refers to a set of one or more attributes that can uniquely identify each row or record in a table. Unique key. Those 7 keys are Primary Key, Foreign Feb 1, 1996 · Candidate exact algorithms, mostly based on a breadth-first-search step, are discussed in the database literature in the context of candidate keys [12, 15, 20]. It must uniquely identify tuples in a table and not be null. There can be multiple Candidate Keys in a table, but we will pick just one of them to serve as the Primary Key of the table. PRIMARY KEY The primary key is the most important key in the database. Summary: You will learn in this article, types of DBMS Keys such as Primary Key, Super Key, Candidate Key, Alternate Key, Foreign Key, Composite Key, Unique Key. A candidate key is one of the attributes that is utilized for identifying each table entry. The primary key is a Candidate key chosen to uniquely identify/determine tuples in the table. The concept of the candidate key is Mar 9, 2024 · Alternate Key. There are 7 main keys in database management systems. A very simple algorithm to find all the candidate keys from the set of all the possible keys and superkeys is the following (in pseudocode): Input: A set SK of all the (candidate keys and) superkeys of a relation R. Indexing: A candidate key is a set of attributes (or attribute) which Oct 9, 2019 · artist_name -> artist_genre. These examples will illustrate the different types of candidate keys and how they can uniquely identify records in a table: Example 1: Students Table. furthermore, every table has to have at Mar 19, 2024 · Additionally, candidate keys enforce relationships between tables, ensuring data integrity and maintaining overall database consistency. Going back to the 1st list of superkeys (i. Jul 18, 2021 · Sementara kunci yang tidak dipilih maka akan dijadikan sebagai alternate key. Designing candidate keys is a fundamental step in database schema design, as they lay the groundwork for establishing the primary means of identifying records within a table. [3] For example, in an employee schema with attributes employeeID , name , job , and departmentID , if employeeID values are unique then employeeID combined with any or all of the other attributes can uniquely identify Apr 16, 2023 · A key is also used when we want to establish relationships between the different columns and tables of a relational database. Examples. The primary key is indicated in the ER model by underlining the attribute. Let K = SK. EmployeeID and EmployeeEmail, both can be a Primary key; therefore both are candidate keys. When looking at a table, you might recognize that there are several columns that could serve as the Primary Key column if Mar 15, 2022 · The candidate key of a relation is all the possible ways through which we can identify a row or a tuple in DBMS. uniquely identifies any data row), then the previous key was not minimal. Jun 28, 2023 · In this article, we will find the attribute closure and also we will find the candidate keys using the functional dependency. Candidate is the smallest sub set of super key. You can use two types of databases: Built-in databases: You can view and manage applicants’ information when you post a job on a platform like LinkedIn Delve into the world of SQL keys with this comprehensive guide. Correctly parses user input for relation schema, functional dependencies, and multivalued dependencies. Given a universal relation scheme, R, and a set of functional dependencies, ÿ,itis essential to determine correctly all candidate keys of R. That means we can either have Emp_Id or Emp_Number as primary key. Learn about primary keys, foreign keys, unique keys, candidate keys, and composite keys, along with their functions and properties. Hence, they cannot form the candidate keys. Primary key values always must be Jan 31, 2022 · Here is an example of a Key within a Relational Database: Image Source. Aug 1, 2021 · The ER diagram is a way to model a database in an organized and efficient way. Above, Student_ID, Student_Enroll and Student_Email are the candidate keys. Thereafter, by using Jan 11, 2024 · Primary keys are central to relational database design, while candidate keys, alternate keys, and surrogate keys provide flexibility and adaptability to different scenarios. Herein, we introduce an An Efficient Algorithm to Compute the Candidate Keys of a Relational Database Schema HOSSEIN SAIEDIAN AND THOMAS SPENCER Department of Computer Science, University of Nebraska at Omaha, Omaha, NE 68182, USA email: hossein@cs. A candidate key is an attribute or a set of attributes that uniquely identify a tuple. Lastly, the usage of candidate keys and primary keys in database design and query optimization also differs. When defining a candidate key, it must Apr 30, 2024 · Candidate Key – Well, what is a candidate key in SQL. Apr 24, 2024 · Choosing the Right Candidate Key . Jun 27, 2023 · Contoh Candidate Key Database. Out of all the Candidate keys that can be possible for a table Dec 1, 2011 · PhoneNumber, StudentNumber, FamilyName. For the uninitiated, exploring the use of these database objects starts with Candidate Key-. Oct 19, 2010 · 5. We will look into this topic in detail. Candidate key. Uniqueness – T he key should be unique, and it should be not subject to change. Candidate Key. A candidate key is a reference point that works in a database in much the same way that a passport works for a traveler. A candidate key is selected by the designer to uniquely Jan 18, 2019 · Candidate key of the table is a collection of all possible primary keys in it. I have been getting lot of comments regarding the confusion between super key and candidate key. Mar 26, 2024 · Super Key. This is because the candidate keys are chosen out of the super keys. The algorithm exploits the 'arrangement' of attributes in the Sep 22, 2020 · A key is a column, or group of columns, in a database management system (DBMS) that uniquely identifies every row in a table. Suppose we make AB the primary key. Let’s consider an example to understand candidate keys better Dec 29, 2022 · Primary key. จาก Table Employees เราจะได้ Candidate Key ทั้งหมดเป็นดังนี้. Consider we have a table Orders with three attributes Customer id May 19, 2016 · I am in the same exam as you, I have asked Paolo what is meant by this: Minimal key and candidate key determine all other attributes in a relationship. Various super keys together makes the criteria to select the candidate keys. A candidate key is also known as a "unique identifier" or "primary key. A candidate key SQL is a column or a set of columns that can qualify as a primary key in the database. Primary Key: It is a candidate key that is chosen by the database designer to identify entities with in an entity set. It is the business that has the knowledge about their entities (things of importance) and what kind of unique information that separate them (invoice numbers, customer IDs, and so on). Super Key 4. But the vice-versa isn’t true. Using our earlier examples, these would be candidate keys for a “customer” table: Social Security Number. Every database designer should be aware of how to identify candidate keys and how to choose the right one for their table. When you first start making E-R diagrams, the number of different choices for keys can be overwhelming. You can use the Keys to extract or fetch rows from a table as and when required. Candidate Key is a Super Key whose no proper subset is a super key, i. You could also use [name, id] as a (compound, multi-column) key. Candidate key: we can say minimal super key is candidate key. It's perfectly sensible for a table to have more than one candidate key enforced in it if that's necessary to ensure some data is not duplicated. A candidate key composed of two or more fields is known as a composite candidate key, and you'll write "CCK" next to the names of the fields that make up the key. Apr 11, 2022 · Kata Candidate Key ini merupakan salah satu dari kumpulan terminologi “Risk Management dengan subkategori Database” dalam bidang teknologi yang dimulai dengan abjad atau awalan C. e. Artikel ini di-update pada bulan Jun tahun 2024. Sep 7, 2023 · Examples of Candidate Keys in a Database Table. Normalization: By selecting a primary key from the available candidate keys, databases can be normalized to Mar 24, 2022 · Learn the basics of database keys with this easy-to-follow tutorial. Database Management Systems (DBMS) are integral in organizing and managing data efficiently. Candidate keys can be chosen based on various factors, such as uniqueness and minimalism, while the primary key selection requires additional considerations, such as stability and suitability for establishing relationships. Dec 6, 2021 · A Candidate Key is a column or group of columns we can use to uniquely identity a row in a table. b. However, from AB→C and CD→E we can also derive that ABD→E. OR. Primary keys and candidate keys play a crucial role in relational database design. 3) Primary key or Candidate keys can be either single column or combination of multiple columns in a table. More precisely, we define port graph rewriting rules and strategies that implement a candidate key definition and Ullman's algorithm to decompose a relation schema into lossless 3NF . Properties of a candidate key. Oct 31, 2016 · It just means that you remove one attribute/column from your key. 2. Feb 27, 2014 · One can describe a candidate key as a super key that contains only the minimum number of columns necessary to determine uniqueness. Example. Let me give you a clear explanation. For instance, in a Students table, possible Super key: super key is a set of atttibutes in a relation (table). There can be multiple Candidate keys in a table in relation to the database e. Dec 11, 2018 · Super key vs Candidate Key. My present article revolves around the two types of keys. 1. First, the FD graph is drawn from the set of functional dependencies in a relational scheme. Understanding the World of DBMS: All About Keys. Number of Keys. Customer ID. In a nutshell, the candidate key is the minimal set of super keys. OR A Apr 1, 2023 · Introduction. Oracle, MySQL, Sybase, or MSSQL but only one primary key is permitted. list the candidate keys of R b. Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. Surrogate Key. May 16, 2024 · Each candidate key ensures that no two rows in the table can have the same combination of values for the candidate key columns. Candidate Key is a subset of a super key. And can uniquely define each and every tupple. EF→G and FG→E. In other words, a candidate key is a minimal set of attributes that can uniquely identify each record in a table. 3. Its primary function is to enable the precise and unambiguous identification of individual records, ensuring data integrity and facilitating efficient retrieval. In the field of SQL, a candidate key is a set of one or more columns that can uniquely identify a row within a table. determine if R is in BCNF or 3NF. Relational Database Keys have various forms of constraint to conform to such as columns, which cannot hold duplicate values or null values. When you have two or more composite candidate Abstract. unomaha. These keys play a crucial role in ensuring data integrity, optimizing queries, and establishing relationships between tables. And let us consider an example: 1. A minimal super key is called as a candidate key. The decision is made by DBA (Database administrator) May 27, 2021 · An alternate key is a function of all candidate keys except the primary key. เช่น Super Key ในข้อ 2 EmpID + FirstName Dec 16, 2015 · 2. Find out what are primary, foreign, candidate, super, surrogate and natural keys in RDBMS. Composite Key. Let’s explore some examples of candidate keys in a database table. which contain only those attributes which are required/needed to uniquely identify tuples. Mar 20, 2023 · A candidate key is a conglomerate of attributes that identify a database record in a unique way without referencing any other key data from the database. A key is a way to categorize attributes in an E-R diagram. According to the definition (candidate key is a minimal key for which the proper subset must not contain a key), for example, the subset of ABD contains the keys AD, and BD which are keys. It is possible to have multiple candidate keys in a relation. , and to help build a relationship with them and hire them later for different roles. Hence, the candidate key is an important concept for the design of the schema of a database. Unique key looks very similar to primary key but they’re not and have a very different usage altogether. All candidate keys serve the same purpose: to ensure data integrity by preventing duplicate data. A candidate key (or minimal superkey) is a superkey that can't be reduced to a simpler superkey by removing an attribute. In other words, it is a potential primary key. Jun 15, 2017 · An Introduction to Candidate Keys. Output: The set K of all the candidate keys of SK. Sebelumnya, kita dapat memetakan/menormalisasi table diatas menjadi seperti dibawah ini: Maka dapat diperoleh: a) Tabel Konsumen. A compound key is a composite key for which each attribute that makes up the key is a foreign key in its own right. The primary key is usually just the candidate key. Those attributes which appears in some candidate key are called as prime attributes. This holds for all the other combinations. aq wa np kn rt ff re jx fu qn