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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 (a duplicate entry is not valid in a unique column). 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 ...
This list includes SQL reserved words – aka SQL reserved keywords, [1] [2] as the SQL:2023 specifies and some RDBMSs have added. Reserved words in SQL and related products In SQL:2023 [ 3 ]
Therefore, a relation can have multiple candidate keys, each with a different number of attributes. [2] Specific candidate keys are sometimes called primary keys, secondary keys or alternate keys. The columns in a candidate key are called prime attributes, [3] and a column that does not occur in any candidate key is called a non-prime attribute.
A data visualisation tool that originally shipped as part of SQL Server 2012, later an add-in for Microsoft Excel [142] SQL14 SQL Server 2014 Version 12 [143] Hekaton: SQL Server In-Memory OLTP In-memory database engine built into SQL Server 2014 [144] SQL16 SQL Server 2016 Version 13 [145] Helsinki SQL Server 2017 Version 14 [146] [147] Seattle
show formulas K show commas W col1 col2 width set column widths N fontid size font to use P index Excel cell format, number of the P record (e.g. P0 means the first P record, which is usually declared as P;PGeneral S style style The following characters can be part of style I italic D bold T gridline top L gridline left B gridline bottom R ...
In the relational model of databases, a primary key is a designated attribute that can reliably identify and distinguish between each individual record in a table.The database creator can choose an existing unique attribute or combination of attributes from the table (a natural key) to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose ...
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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 databases, a foreign key is subject to an inclusion dependency constraint that the tuples consisting of the foreign key attributes in one relation, R, must also exist in some other (not necessarily distinct) relation, S; furthermore that those ...