Mikhail Gorbachev's policies of glasnost and perestroika had profound and unintended effects on the Soviet Union. In fact, many historians suggest these reforms led directly to the fall of communism and the breakup of the Soviet Union.
In SQL Server, you create a surrogate key by assigning an identity property to a column that has a number data type. A natural key is a naturally occurring descriptor of the data and one of a table's attributes that has no duplicate values. When you use a natural key as a table's primary key, each of the table's rows is uniquely identified.
When you open a cursor variable with the OPEN FOR statement, PL/SQL evaluates any variables in the query and uses those values when identifying the result set. Changing the values of the variables later does not change the result set.f you process a query result set by looping through it and running another query for each row, then you can improve performance by removing the second query from inside the loop and making it a subquery of the first query. For more information about subqueries, see Oracle Database SQL Language Reference.