Cross join is defined as the Cartesian product of records from the tables present in the join. Cross join will produce result which combines each row from the first table with the each row from the second table.
A class invariant is a condition that defines all valid states for an object. It is a logical condition to ensure the correct working of a class. Class invariants must hold when an object is created, and they must be preserved under all operations of the class. In particular all class invariants are both preconditions and post-conditions for all operations or member functions of the class.
A copy constructor constructs a new object by using the content of the argument object. An overloaded assignment operator assigns the contents of an existing object to another existing object of the same class.
Privileges are the rights to execute SQL statements – means Right to connect and connect. Grants are given to the object so that objects can be accessed accordingly. Grants can be provided by the owner or creator of an object.
Attributes of Cursor are :
%FOUND :
%NOT FOUND :
%ISOPEN :
%ROWCOUNT :
Hash Cluster is a technique used to store the table for faster retrieval. Apply hash value on the table to retrieve the rows from the table.
COALESCE function is used to return the value which is set to be not null in the list. If all values in the list are null, then the coalesce function will return NULL.
Coalesce(value1, value2,value3,…)
An alert is a window which appears in the center of the screen overlaying a portion of the current display.
Duplicate rows in the table can be deleted by using ROWID.
RAW datatype is used to store values in binary data format. The maximum size for a raw in a table in 32767 bytes.
The WITH CHECK option clause specifies check level to be done in DML statements. It is used to prevent changes to a view that would produce results that are not included in the sub query.
A BLOB data type is a varying length binary string which is used to store two gigabytes memory. Length should be specified in Bytes for BLOB.
A cursor variable is associated with different statements which can hold different values at run time. A cursor variable is a kind of reference type.
Rename is a permanent name given to a table or a column whereas Alias is a temporary name given to a table or column. Rename is nothing but replacement of name and Alias is an alternate name of the table or column.
Before the function definition, with the keyword inline, a function is prefixed it is said to be an inline function.
An integrity constraint is a declaration defined a business rule for a table column. Integrity constraints are used to ensure accuracy and consistency of data in a database. There are types – Domain Integrity, Referential Integrity and Domain Integrity.
IN, OUT and INOUT are the modes of parameters that can be passed to a procedure.
An inline function is a function that is expanded inline when invoked.ie. the compiler replaces the function call with the corresponding function code. An inline function is a function that is expanded in line when it is invoked. That is the compiler replaces the function call with the corresponding function code (similar to macro).
Each cursor in Oracle has set of attributes which enables an application program to test the state of the cursor. The attributes can be used to check whether cursor is opened or closed, found or not found and also find row count.
A privilege is nothing but right to execute an SQL query or to access another user object. Privilege can be given as system privilege or user privilege.
[sql]GRANT user1 TO user2 WITH MANAGER OPTION;[/sql]
Varchar can store upto 2000 bytes and varchar2 can store upto 4000 bytes. Varchar will occupy space for NULL values and Varchar2 will not occupy any space. Both are differed with respect to space.
A GROUP BY clause can be used in select statement where it will collect data across multiple records and group the results by one or more columns.
A conversion constructor declared with the explicit keyword. The compiler does not use an explicit constructor to implement an implied conversion of types. It’s purpose is reserved explicitly for construction. Explicit constructors are simply constructors that cannot take part in an implicit conversion.
Row can be fetched from table by using ROWID. Using ROW ID is the fastest query method to fetch data from the table.
View is a logical table which based on one or more tables or views. The tables upon which the view is based are called Base Tables and it doesn’t contain data.
Iterators are like pointers. They are used to access the elements of containers thus providing a link between algorithms and containers. Iterators are defined for specific containers and used as arguments to algorithms.
12 is the maximum number of triggers that can be applied to a single table.
A table is set to be key preserved table if every key of the table can also be the key of the result of the join. It guarantees to return only one copy of each row from the base table.
The DUAL table is a one-column table present in oracle database. The table has a single VARCHAR2(1) column called DUMMY which has a value of ‘X’.
If the function is defined outside the class, this one is used to associate function definition to the class. It is also used to resolve the scope of global variables.
Sub Query is also called as Nested Query or Inner Query which is used to get data from multiple tables. A sub query is added in the where clause of the main query.
There are two different types of subqueries:
Correlated sub query : A Correlated sub query cannot be as independent query but can reference column in a table listed in the from list of the outer query.
Non-Correlated subquery : This can be evaluated as if it were an independent query. Results of the sub query are submitted to the main query or parent query.
VArray is an oracle data type used to have columns containing multivalued attributes and it can hold bounded array of values.
The NVL function is used to replace NULL values with another or given value.
Example is – NVL(Value, replace value)
Yes, we can store pictures in the database by Long Raw Data type. This datatype is used to store binary data for 2 gigabytes of length. But the table can have only on Long Raw data type.
The USING clause is used to specify with the column to test for equality when two tables are joined.
[sql]Select * from employee join salary using employee ID[/sql]
Employee tables join with the Salary tables with the Employee ID.
Duplicate rows can be removed by using the keyword DISTINCT in the select statement.
Translate is used for character by character substitution and Replace is used substitute a single character with a word.
SET operators are used with two or more queries and those operators are Union, Union All, Intersect and Minus.
Merge statement is used to select rows from one or more data source for updating and insertion into a table or a view. It is used to combine multiple operations.
The function declaration should be preceded by the keyword friend. The function definitions does not use either the keyword or the scope operator ::. The functions that are declared with the keyword friend as friend function. Thus, a friend function is an ordinary function or a member of another class.
Describe <Table_Name> is used to get the field details of a specified table.
Nested table is a data type in Oracle which is used to support columns containing multi valued attributes. It also hold entire sub table.