Nt1320 Unit 2

Good Essays
4. SQL-92 was a major revision and was structured into three levels: Entry, Intermediate, and Full. SQL:1999 established the core-level conformance, which should be met before any different level of conformance is achieved; core-level conformance needs are unchanged in SQL:2008. In addition to fixes and enhancements of SQL:1999, SQL:2003 introduced a new set of SQL/XML standards, three new knowledge sorts, various new inbuilt functions, and improved methods for generating values mechanically. SQL:2006 refined these additions and made them additional compatible with XQuery, the XML query language printed by the world Wide net association (W3C). At the time of this writing, most database management systems claim SQL:1992
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SQL commands can be classified into three varieties. First, there are data definition language (DDL) commands. These commands are used to create, alter, and drop tables, views, and indexes. Next, there are data manipulation language (DML) commands. Many think about the DML commands to be the core commands of SQL. These commands are used for updating, inserting, modifying, and querying the data within the database
10. By using SQL queries with any RDBMS, it is possible to create virtual tables, or dynamic views, whose contents materialize once documented. These views may typically be manipulated in the same way as a base table will be manipulated, through SQL SELECT queries. Materialized views, which area unit stored physically on a disk and refreshed at acceptable intervals or events, may also be used.
12. Consider a situation in that 50 programs all use the Customer table. Suppose that the Pine Valley Furniture Company database evolves to support new functions that need the Customer table to be renormalized into 2 tables. If these 50 programs refer directly to the Customer base table, they will all have to be changed to refer to one among the two new tables or to joined tables. But if these programs all use the view on this base table, then only the view has to be create, saving considerable reprogramming
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GROUP BY is significantly helpful once paired with aggregate functions, such as SUM or COUNT. GROUP BY divides a table into subsets (by groups); then an aggregate function will be used to give outline data for that group. When a group BY is included, the columns allowed to be specified in the select clause are restricted.
20. IN is particularly useful in SQL statements that use subqueries, the use of IN is also very consistent with the set nature of SQL. Very simply, the list (set of values) inside the parentheses when IN will be literals, as illustrated here, or can be a choose statement with a single result column, the result of which is able to be plugged in because the set of values for comparison.
22. SQL:1999 included the capability of adding a LIKE clause to the create TABLE statement to allow for the copying of the present structure of one or additional tables into a new table.
24. The SQL:2008 standard has enclosed a new keyword, MERGE, that makes updating a table easier. Many database applications would like to update master tables with new data. A Purchases T table, for example, might include rows with data regarding new products and rows that change the standard value of existing

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