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Articles by Nitya Raut
Page 8 of 16
What is the meaning of 'empty set' in MySQL result set?
If there is ‘empty set’ in the result set of MySQL query then it means that MySQL is returning no rows and no error also in the query. It can be understood with the help of the following example −mysql> Select * from Student_info WHERE Name = 'ABCD'; Empty set (0.00 sec)We can see the empty set and execution time as output. It means that the query is correct but the MySQL table is not having the name ‘ABCD’.
Read MoreIn MySQL, how we can write Multiple-line statement?
We can write multiple-line statements because MySQL determines the end of a statement by looking for the termination semicolon, not by looking for the end of the input line.Examplemysql> Select * -> from -> stock_item; +------------+-------+----------+ | item_name | Value | Quantity | +------------+-------+----------+ | Calculator | 15 | 89 | | Notebooks | 63 | 40 | | Pencil | 15 | 40 | | Pens | 65 | 32 | | Shirts | 13 ...
Read MoreWhat are the advantages and disadvantages of using MySQL stored procedures?
There are numerous advantages and disadvantages of using MySQL stored procedures which are as follows −MySQL Stored Procedure AdvantagesFollowings are the advantages of using MySQL Stored Procedures −Increasing the performance of applications − As we know that after creating the stored procedure it is compiled and stored in the database. But MySQL implements stored procedures slightly different which helps in increasing the performance of the applications. MySQL stored procedures are compiled on demand. After compiling a stored procedure, MySQL puts it into a cache. And MySQL maintains its own stored procedure cache for every single connection. If an application uses ...
Read MoreWhich MySQL query can be used with the help of which we can see the list of MySQL databases?
With the help of following MySQL query, we can see the list of MySQL database −mysql> SELECT schema_name FROM information_schema.schemata; +--------------------+ | schema_name | +--------------------+ | information_schema | | gaurav | | mysql | | performance_schema | | query | | query1 | | sys | | tutorials | +--------------------+ 8 rows in set (0.00 sec)We can also use WHERE clause with this query as follows −mysql> SELECT schema_name FROM information_schema.schemata WHERE schema_name LIKE '%schema' OR schema_name LIKE '%s'; +--------------------+ | schema_name | +--------------------+ | information_schema | | performance_schema | | sys | | tutorials | +--------------------+ 4 rows in set (0.00 sec)
Read MoreHow MySQL LEFT JOIN can be used to simulate the MySQL MINUS query?
Since we cannot use MINUS query in MySQL, we will use LEFT JOIN to simulate the MINUS query. It can be understood with the help of the following example:ExampleIn this example, we are two tables namely Student_detail and Student_info having the following data −mysql> Select * from Student_detail; +-----------+---------+------------+------------+ | studentid | Name | Address | Subject | +-----------+---------+------------+------------+ | 101 | YashPal | Amritsar | History | | 105 | Gaurav | Chandigarh | Literature | | 130 | Ram | Jhansi ...
Read MoreHow can we store a value in user-defined variable?
We can store a value in a user-defined variable in a statement and then refer to it afterward in other statements. Followings are the ways to store a value in user-defined variable −With SET statementwe can store a user-defined variable by issuing a SET statement as follows −SyntaxSET @var_name = expr[, @var_name = expr]…In this @var_name is the variable name which consists of alphanumeric characters from current character set. We can use either = or := assignment operator with SET statement.For example following queries can store the user variables with SET statement −mysql> SET @value = 500; Query OK, 0 ...
Read MoreWhat MySQL returns when we alter AUTO_INCREMENT value which is less than current sequence number?
When we use AUTO_INCREMENT on a MySQL column, the sequence number always increases in ascending order starting from the default value 1 or from the value we specify.That is the reason, MySQL does not allow changing the AUTO_INCREMENT value to a value which is less than the current sequence number. It can be understood with the help of the following example −ExampleIn this example suppose we have a table named ‘emp1’ and while creating the table we specify the AUTO_INCREMENT VALUE to 100. Hence after inserting the values in table, the sequence would start from 100 onwards as can be ...
Read MoreWebsites every Java developer should bookmark
There are many sites which are a good resource to learn java. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/
Read MoreHow to read and parse CSV files in C++?
You should really be using a library to parsing CSV files in C++ as there are many cases that you can miss if you read files on your own. The boost library for C++ provides a really nice set of tools for reading CSV files. For example, example#include vector parseCSVLine(string line){ using namespace boost; std::vector vec; // Tokenizes the input string tokenizer tk(line, escaped_list_separator ('', ', ', '"')); for (auto i = tk.begin(); i!=tk.end(); ++i) ...
Read MoreWhat is the ?-->? operator in C++?
There is no such operator in C++. Sometimes, we need to create wrapper types. For example, types like unique_ptr, shared_ptr, optional and similar. Usually, these types have an accessor member function called .get but they also provide the operator→ to support direct access to the contained value similarly to what ordinary pointers do.The problem is that sometimes we have a few of these types nested into each other. This means that we need to call .get multiple times or to have a lot of dereference operators until we reach the value.Something like this −wrapper wp; wp.get().get().length(); wp.get()->length();This can be a ...
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