Technology Questions

JDK is Java Development Kit which is for development purpose and it includes execution environment also.

JVM is Java Virtual Machine which is a run time environment for the compiled java class files .Hence you will not be able to compile your source files using a JVM.

Aggregate functions in SQL are used to perform calculation on data. These functions are inbuilt in SQL and return a single value.

SUM( )

SUM function returns the sum or addition of all NOT NULL values of a column. For e.g. I have a Table employee with the fields id, name, salary and I want the sum of all salaries, I can use SUM function as shown
SELECT SUM(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 63,000

AVG( )

 
AVG function returns the average of all NOT NULL values of a column. For e.g. I have a Table employee with the fields id, name, salary and I want the average of all salaries, I can use AVG function as shown
SELECT AVG(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 21,000

COUNT( )

COUNT function returns the number of rows or values of a table. For e.g. I have a Table employee with the fields id, name, salary and I want the count of all rows, I can use COUNT function as shown
SELECT COUNT(*) from employee;

Max ( ) and Min ( )

MAX function returns the largest value of a column in a table. For e.g. I have a Table employee with the fields id, name, salary and I want the maximum salary of an employee, I can use MAX function as shown
SELECT MAX(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 22,000

MIN function returns the smallest value of a column in a table. For e.g. I have a Table employee with the fields id, name, salary and I want the minimun salary of an employee, I can use MIN function as shown
SELECT MIN(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 20,000

TelephonyManager class can be used to get the IMEI number. It provides access to information about the telephony services on the device.

Code

        TelephonyManager mTelephonyMgr = (TelephonyManager)

        getSystemService(Context.TELEPHONY_SERVICE);

        String imei = mTelephonyMgr.getDeviceId();

- If the table structure is changed ( a field is added ), the program will have to be modified.

- Program might retrieve the columns which it might not use, leading on I/O over head.

- The chance of an index only scan is lost.

a nonmatching index scan if ACCESSTYPE = 1

According to one-definition rule, C++ constructs must be identically defined in every compilation unit they are used in. 

As per ODR, two definitions contained in different source files are called to be identically defined if they token-for-token identical. The tokens should have same meaning in both source files. 

Identically defined doesn’t mean character-by-character equivalence. Two definitions can have different whitespace or comments and yet be identical.