Matches in DBpedia 2014 for { <http://dbpedia.org/resource/Null_(SQL)> ?p ?o. }
Showing items 1 to 35 of
35
with 100 items per page.
- Null_(SQL) abstract "Null is a special marker used in Structured Query Language (SQL) to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd, SQL Null serves to fulfill the requirement that all true relational database management systems (RDBMS) support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek omega (ω) symbol to represent Null in database theory. NULL is also an SQL reserved keyword used to identify the Null special marker.Null has been the focus of controversy and a source of debate because of its associated three-valued logic (3VL), special requirements for its use in SQL joins, and the special handling required by aggregate functions and SQL grouping operators. Computer science professor Ron van der Meyden summarized the various issues as: "The inconsistencies in the SQL standard mean that it is not possible to ascribe any intuitive logical semantics to the treatment of nulls in SQL." Although various proposals have been made for resolving these issues, the complexity of the alternatives has prevented their widespread adoption.For people new to the subject, a good way to remember what null means is to remember that in terms of information, "lack of a value" is not the same thing as "a value of zero"; similarly, "lack of an answer" is not the same thing as "an answer of no". For example, consider the question "How many books does Juan own?" The answer may be "zero" (we know that he owns none) or "null" (we do not know how many he owns, or doesn't own). In a database table, the column reporting this answer would start out with a value of null, and it would not be updated with "zero" until we have ascertained that Juan owns no books.SQL null is a state (unknown) and not a value. This usage is quite different from programming languages, where null means not assigned to a particular instance.".
- Null_(SQL) thumbnail Db_null.png?width=300.
- Null_(SQL) wikiPageExternalLink view_bug.do?bug_id=4032732.
- Null_(SQL) wikiPageExternalLink paper8.pdf.
- Null_(SQL) wikiPageExternalLink sql.ps.
- Null_(SQL) wikiPageExternalLink IJCS_35_3_08.pdf.
- Null_(SQL) wikiPageExternalLink null.html.
- Null_(SQL) wikiPageExternalLink treatment-of-nulls-by-oracle-sql.html.
- Null_(SQL) wikiPageExternalLink the-nature-of-null.
- Null_(SQL) wikiPageExternalLink www.thethirdmanifesto.com.
- Null_(SQL) wikiPageExternalLink Rubinson.2007.Nulls_Three-Valued_Logic_and_Ambiguity_in_SQL.pdf.
- Null_(SQL) wikiPageExternalLink p23.grant.pdf.
- Null_(SQL) wikiPageID "2002540".
- Null_(SQL) wikiPageRevisionID "598107182".
- Null_(SQL) hasPhotoCollection Null_(SQL).
- Null_(SQL) subject Category:Articles_with_example_SQL_code.
- Null_(SQL) subject Category:SQL_keywords.
- Null_(SQL) subject Category:Unknown_content.
- Null_(SQL) comment "Null is a special marker used in Structured Query Language (SQL) to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd, SQL Null serves to fulfill the requirement that all true relational database management systems (RDBMS) support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek omega (ω) symbol to represent Null in database theory.".
- Null_(SQL) label "NULL (SQL)".
- Null_(SQL) label "Null (SQL)".
- Null_(SQL) label "Null (SQL)".
- Null_(SQL) label "Null (SQL)".
- Null_(SQL) label "Null (SQL)".
- Null_(SQL) label "空值 (SQL)".
- Null_(SQL) sameAs Null_(SQL).
- Null_(SQL) sameAs Null_(SQL).
- Null_(SQL) sameAs Null_(SQL).
- Null_(SQL) sameAs Null_(SQL).
- Null_(SQL) sameAs m.06d7bk.
- Null_(SQL) sameAs Q371029.
- Null_(SQL) sameAs Q371029.
- Null_(SQL) wasDerivedFrom Null_(SQL)?oldid=598107182.
- Null_(SQL) depiction Db_null.png.
- Null_(SQL) isPrimaryTopicOf Null_(SQL).
