Everything about Unique key
Concept in relational database design
In relational database management systems, a unique key is a candidate key. All the candidate keys of a relation can uniquely identify the records of the relation, but only one of them is used as the primary key of the relation. The remaining candidate keys are called unique keys because they can uniquely identify a record in a relation. Unique keys can consist of multiple columns. Unique keys are also called alternate keys. Unique keys are an alternative to the primary key of the relation. In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates. Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not typically used to join multiple tables. Wikipedia →
🧭 Start here: a 6-step reading path
- Read the overview: Unique keyA 5-minute orientation
- Skim a recent paper: Pu-erh tea unique aroma: Volatile components, evaluation methods and metabolic mechanism of key odor-active compoundsInfluential work since 2022
- Pick up a classic book: Drug calculationsThe most-reprinted book on the subject
- Read the landmark paper: Fungi took a unique evolutionary route to multicellularity: Seven key challenges for fungal multicellular lifeCited 58 times
- Go sideways: Primary keyA closely related topic
- Go sideways: Relational modelA closely related topic
📖 Definitions
Noun A set of one or more than one columns or fields of a table that uniquely identifies a record in a database table.
🗂️ The subject at a glance
🏆 Landmark papers (most cited)
Fungi took a unique evolutionary route to multicellularity: Seven key challenges for fungal multicellular life
Unique Temporal Change Is the Key to Attentional Capture
Aluminum batteries: Unique potentials and addressing key challenges in energy storage
The key to top-level endurance running performance: a unique example: Table 1
Aminovinyl Cysteine Containing Peptides: A Unique Motif That Imparts Key Biological Activity
Secure image cryptosystem with unique key streams via hyper-chaotic system
A key region of molecular specificity orchestrates unique ephrin-B1 utilization by Cedar virus
Context Is Key: Delineating the Unique Functions of IFNα and IFNβ in Disease
🆕 Influential since 2022
Pu-erh tea unique aroma: Volatile components, evaluation methods and metabolic mechanism of key odor-active compounds
Unique thermal expansion properties of water key to the formation of sea ice on Earth
Transcriptional landscape of Kaposi sarcoma tumors identifies unique immunologic signatures and key determinants of angiogenesis
Promote hydroxyl radical and key intermediates formation for deep toluene mineralization via unique electron transfer channel
Spatial transcriptomics reveals unique metabolic profile and key oncogenic regulators of cervical squamous cell carcinoma
📚 Books worth reading
Drug calculationsMeta Brown Seltzer, Joyce L. Mulholland · 1988
Ranked by number of editions on Open Library, a rough measure of how lasting a book is.
🔗 Related topics
- Primary key In the relational model of databases, a primary key is a designated set of attributes (column(s)) that can reliably identify and distinguish between each…
- Relational model The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in…
- Relational database A relational database (RDB) is a database based on the relational model of data, as proposed by E. F. Codd in 1970. A Relational Database Management System…
- Referential integrity Referential integrity is a property of data stating that all its references are valid. In the context of relational databases, it requires that if a value…
- Foreign key A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables. In the context of relational…
- Data definition language In the context of SQL, data definition language (DDL) is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements…
- Null (SQL) In the SQL database query language, null or NULL is a special marker used to indicate that a data value does not exist in the database. Introduced by the…
- Surrogate key A surrogate key (or synthetic key, pseudokey, entity identifier, factless key, or technical key[citation needed]) in a database is a unique identifier…