enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Cardinality (SQL statements) - Wikipedia

    en.wikipedia.org/wiki/Cardinality_(SQL_statements)

    An example of a data table column with high-cardinality would be a USERS table with a column named USER_ID. This column would contain unique values of 1-n. Each time a new user is created in the USERS table, a new number would be created in the USER_ID column to identify them uniquely. Since the values held in the USER_ID column are unique ...

  3. Unique key - Wikipedia

    en.wikipedia.org/wiki/Unique_key

    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 typically used to join multiple tables.

  4. Primary key - Wikipedia

    en.wikipedia.org/wiki/Primary_key

    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 ...

  5. Foreign key - Wikipedia

    en.wikipedia.org/wiki/Foreign_key

    The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table. [4] In database relational modeling and implementation, a candidate key is a set of zero or more attributes, the values of which are guaranteed to be unique for each tuple (row) in a relation.

  6. Referential integrity - Wikipedia

    en.wikipedia.org/wiki/Referential_integrity

    A table (called the referencing table) can refer to a column (or a group of columns) in another table (the referenced table) by using a foreign key. The referenced column(s) in the referenced table must be under a unique constraint, such as a primary key. Also, self-references are possible (not fully implemented in MS SQL Server though [5]).

  7. Surrogate key - Wikipedia

    en.wikipedia.org/wiki/Surrogate_key

    A surrogate key is frequently a sequential number (e.g. a Sybase or SQL Server "identity column", a PostgreSQL or Informix serial, an Oracle or SQL Server SEQUENCE or a column defined with AUTO_INCREMENT in MySQL). Some databases provide UUID/GUID as a possible data type for surrogate keys (e.g. PostgreSQL UUID [3] or SQL Server ...

  8. Puzzle solutions for Wednesday, Dec. 4, 2024

    www.aol.com/news/puzzle-solutions-wednesday-dec...

    Find the Words. Use the flags on the beach (Distributed by Creators Syndicate) Kubok. This article originally appeared on USA TODAY: Online Crossword & Sudoku Puzzle Answers for 12/04/2024 - USA ...

  9. Select (SQL) - Wikipedia

    en.wikipedia.org/wiki/Select_(SQL)

    Without an ORDER BY clause, the order of rows returned by an SQL query is undefined. The DISTINCT keyword [5] eliminates duplicate data. [6] The following example of a SELECT query returns a list of expensive books. The query retrieves all rows from the Book table in which the price column contains a value greater

  1. Related searches how to find unique records in sql table in mysql column with different user

    unique key in databaseunique key for relational database