enow.com Web Search

Search results

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

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

    The joined table retains each row—even if no other matching row exists. Outer joins subdivide further into left outer joins, right outer joins, and full outer joins, depending on which table's rows are retained: left, right, or both (in this case left and right refer to the two sides of the JOIN keyword).

  3. Relational database - Wikipedia

    en.wikipedia.org/wiki/Relational_database

    The join operation defined for relational databases is often referred to as a natural join (⋈). In this type of join, two relations are connected by their common attributes. MySQL's approximation of a natural join is the Inner join operator. In SQL, an INNER JOIN prevents a cartesian product from occurring when there are two tables in a query.

  4. SQL - Wikipedia

    en.wikipedia.org/wiki/SQL

    SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...

  5. Associative entity - Wikipedia

    en.wikipedia.org/wiki/Associative_entity

    Associative tables are colloquially known under many names, including association table, bridge table, cross-reference table, crosswalk, intermediary table, intersection table, join table, junction table, link table, linking table, many-to-many resolver, map table, mapping table, pairing table, pivot table (as used in Laravel—not to be ...

  6. Recursive join - Wikipedia

    en.wikipedia.org/wiki/Recursive_join

    The recursive join is an operation used in relational databases, also sometimes called a "fixed-point join". It is a compound operation that involves repeating the join operation, typically accumulating more records each time, until a repetition makes no change to the results (as compared to the results of the previous iteration).

  7. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    Title Authors ----- ----- SQL Examples and Guide 4 The Joy of SQL 1 An Introduction to SQL 2 Pitfalls of SQL 1 Under the precondition that isbn is the only common column name of the two tables and that a column named title only exists in the Book table, one could re-write the query above in the following form:

  8. Merge (SQL) - Wikipedia

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

    Some other database management systems support this, or very similar behavior, through their own, non-standard SQL extensions. MySQL , for example, supports the use of INSERT ... ON DUPLICATE KEY UPDATE syntax [ 5 ] which can be used to achieve a similar effect with the limitation that the join between target and source has to be made only on ...

  9. Block nested loop - Wikipedia

    en.wikipedia.org/wiki/Block_nested_loop

    For example, one variant of the block nested loop join reads an entire page of tuples into memory and loads them into a hash table. It then scans S {\displaystyle S} , and probes the hash table to find S {\displaystyle S} tuples that match any of the tuples in the current page of R {\displaystyle R} .