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  2. Set operations (SQL) - Wikipedia

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

    The INTERSECT operator removes duplicate rows from the final result set. The INTERSECT ALL operator does not remove duplicate rows from the final result set, but if a row appears X times in the first query and Y times in the second, it will appear min ( X , Y ) {\displaystyle \min(X,Y)} times in the result set.

  3. PL/SQL - Wikipedia

    en.wikipedia.org/wiki/PL/SQL

    The purpose of a PL/SQL function is generally used to compute and return a single value. This returned value may be a single scalar value (such as a number, date or character string) or a single collection (such as a nested table or array). User-defined functions supplement the built-in functions provided by Oracle Corporation. [6]

  4. Relational algebra - Wikipedia

    en.wikipedia.org/wiki/Relational_algebra

    The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.

  5. DUAL table - Wikipedia

    en.wikipedia.org/wiki/DUAL_table

    The DUAL table is a special one-row, one-column table present by default in Oracle and other database installations. In Oracle, the table has a single VARCHAR2(1) column called DUMMY that has a value of 'X'. It is suitable for use in selecting a pseudo column such as SYSDATE or USER.

  6. Set intersection oracle - Wikipedia

    en.wikipedia.org/wiki/Set_intersection_oracle

    A set intersection oracle (SIO) is a data structure which represents a collection of sets and can quickly answer queries about whether the set intersection of two given sets is non-empty. The input to the problem is n finite sets. The sum of the sizes of all sets is N (which also means that there are at most N distinct elements). The SIO should ...

  7. List of set identities and relations - Wikipedia

    en.wikipedia.org/wiki/List_of_set_identities_and...

    So for example, would mean () since it would be associated with the logical statement = and similarly, would mean () since it would be associated with = (). Sometimes, set complement (subtraction) ∖ {\displaystyle \,\setminus \,} is also associated with logical complement (not) ¬ , {\displaystyle \,\lnot ,\,} in which case it will have the ...

  8. Help:Advanced table formatting - Wikipedia

    en.wikipedia.org/wiki/Help:Advanced_table_formatting

    Cut cells into parts: Instead of trying to make a super-cell that spans rows/columns, split it into smaller cells while leaving some cells intentionally empty. Use a non-breaking space with   or {} in empty cells to maintain the table structure. Custom CSS styling: Override the wikitable class defaults by explicitly specifying:

  9. Select (SQL) - Wikipedia

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

    Instead of showing hundreds or thousands of rows at the same time, the server is requested only one page (a limited set of rows, per example only 10 rows), and the user starts navigating by requesting the next page, and then the next one, and so on.