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Articles by Arjun Thakur
Page 11 of 75
Does MySQL foreign_key_checks affect the entire database?
The foreign_key_checks are session based. Now, we can say that they are for scope i.e. local or global. Here is an example demo of local or global. Both are scopes and we can set this for session.Let us set the scope −mysql> set foreign_key_checks = 0; Query OK, 0 rows affected (0.00 sec) mysql> set global foreign_key_checks = 0; Query OK, 0 rows affected (0.05 sec)The foreign_key_checks variables are server system variables. Here are some more details −PropertyValueSystem Variableforeign_key_checksScopeGlobal, SessionDynamicYesTypeBooleanDefault ValueONSetting foreign_key_checks to 0It affects data definition statements: DROP SCHEMA drops a schema even if it contains tables that have ...
Read MoreHow to check similarity between two strings in MySQL?
Similarity between two strings can be checked with the help of ‘strcmp()’ function. Here are the conditions.If both strings are equal, then it returns 0.If first string is less than the second string, it returns -1.If first string is greater than the second string, it returns 1.Here is an example.Case 1 − If both strings are equal.The following is the query.mysql > SELECT STRCMP("demo", "demo");The following is the output of the above query.+------------------------+ | STRCMP("demo", "demo") | +------------------------+ | 0 ...
Read MoreWhich one is better in MySQL - NULL or empty string?
The choice depends upon the database. In ORACLE database, an empty string is converted to NULL.In MySQL, the usage of an empty string is better as compared to NULL. It is easy to check for an empty string with some boundary conditions, while this cannot be done with NULL. To find NULL, we need to add an extra condition i.e. ‘IS NULL’We can check that the length of NULL is 0 while length of empty string is 1.To check the length of NULL.mysql>SELECT count(NULL);The following is the output of the above query.+-----------------+ | count(NULL) | +-----------------+ ...
Read MoreAbsolute addressing mode in 8085 Microprocessor
In this mode, the data is directly copied from the given address to the register. This absolute addressing mode is also called a direct addressing mode. For example LDA 3000H: means the data at address 3000H is copied to register A.LDA 4050HLet us consider LDA 4050 Has an example instruction of this type. It is a 3-Byte instruction. The initial content of memory address 4050H is ABH. initial accumulator content is CDH. As after execution A will be initialized with value ABH. Memory location 4050H will still remain with the content ABH. The results of the execution of this instruction ...
Read MoreProgramming the 8259 with no slaves
Now in this topic we assume that 8085 is the processor which is used in this microcomputer system. In this slave, no 8259 slaves are used. We should examine properly before 8259 PIC is used in the microcomputer system for performing the interrupt control application. 8259 is configured in such a fantastic way that is found that a variety of information are provided like for IR0 request IV, interrupts like level or edge-triggered, whether 8259s are used single or many, if ICW4 is in need or not and whether for the interrupt requests masking should be done or not. This ...
Read MoreTimer Class in Java
The Timer Class in Java is a facility for threads to plan tasks for future execution in a background thread. Tasks may be executed a single time or multiple times. The Timer class is thread-safe i.e. the threads of the class do not require external synchronization and can share a single Timer object. A point to be noted is that all constructors start a Timer thread.The Timer Class in Java came into existence since JDK 1.3. This class ascends up to large numbers of concurrently scheduled tasks. Internally, it uses a binary heap in the memory to represent its task ...
Read MoreHow to schedule tasks in Java to run for repeated fixed-delay execution, beginning at the specified time
One of the methods in the Timer class is the void schedule(TimerTask task, Date firstTime, long period) method. This method schedules tasks for repeated fixed-delay execution, beginning at the specified time.In fixed-delay execution, each execution is scheduled with respect to the original execution time of the preceding execution. If an execution is delayed for a particular reason (case in point, garbage collection), the subsequent executions will be delayed as well.Declaration −The java.util.Timer.schedule(TimerTask task, Date firstTime, long period) is declared as follows −public void schedule(TimerTask task, Date firstTime, long period)Here, task is the task to be scheduled, firstTime is the first ...
Read MoreDifference between x++ and x= x+1 in Java programming
x++ automatically handles the type casting where as x= x + 1 needs typecasting in case of x is not an int variable. See the example below.Example Live Demopublic class Tester { public static void main(String args[]) { byte b = 2; //Type casting is required //as 1 is int and b is byte variable b = (byte) (b + 1); System.out.println(b); byte b1 = 2; //Implcit type casting by the compiler b1++; System.out.println(b1); } }Output3 3
Read MoreHow Java objects are stored in memory?
A stack and a heap are used for memory allocation in Java. However, the stack is used for primitive data types, temporary variables, object addresses etc. The heap is used for storing objects in memory.Stacks and heaps in Java are explained in more detail as follows −Stack in JavaStacks are used to store temporary variables, primitive data types etc. A block in the stack exists for a variable only as long as the variable exists. After that, the block data is erased and it can be used for storing another variable.
Read MoreHow to create your own helper class in Java?
A helper class serve the following purposes.Provides common methods which are required by multiple classes in the project.Helper methods are generally public and static so that these can be invoked independently.Each methods of a helper class should work independent of other methods of same class.Following example showcases one such helper class.Examplepublic class Tester { public static void main(String[] args) { int a = 37; int b = 39; System.out.println(a + " is prime: " + Helper.isPrime(a)); System.out.println(b + " is prime: " + Helper.isPrime(b)); } } ...
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