Darabase

Join relations

Join relations – The concept of a joined table (or joined relation) was incorporated to permit users to specify a table resulting from a join operation in the FORM clause of a query. In addition to providing the basic Cartisean product mechanism for joining tuples of relations provided by the earlier versions of SQL. SQL- 92 …

Database set operations

Database set operations Database set operations – As we have ᴖ, ᴗ, – operations in algebra, same we have Union, Intersect and except operations in SQL. Like Union, Intersection and set difference operation in relational-algebra, the tables participating in these operations must be compatible that is, that they must be of the same arity and …

SQL String operations

SQL String operations SQL String operations : SQL provides LIKE operator for performing pattern matching, this is one of the most important features of SQL, and very handy in retrieving data from the existing database. Instead of specifying the entire string, we can specify only some specific part of the match to be found. The following two special …

SQL FROM clause

SQL FROM clause SQL FROM clause by itself defines a Cartesian product of the relations in the clause. Since the natural joint defined in the terms of a Cartesian product a SELECTION, and a PROJECTION, it is relatively simple matter to write SQL expression for the natural join. “For all customers who have a loan …

SQL Group by

SQL Group by SQL Group by : In certain situations we would like to use aggregate functions, which are applicable to a group of set of tuples, rather than a single set of tuples, we specify this using GROUP BY clause. The attribute are attributes given in the GROUP BY clause are used to form …