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Articles by mkotla
Page 7 of 8
What MySQL would return if we refer a user variable which is not assigned any value explicitly?
In case, when we refer a user variable which is not assigned any value explicitly, MySQL would return NULL. In other words, its value would be NULL. Following example would illustrate it −mysql> Select @X, @Y, @Z, @S, @G; +------+-------+----------+------+------+ | @X | @Y | @Z | @S | @G | +------+-------+----------+------+------+ | Ram | Shyam | Students | 5000 | NULL | +------+-------+----------+------+------+ 1 row in set (0.00 sec)We can see from the above result set that @X, @Y, @Z and @S has been assigned values explicitly and they returned the values ...
Read MoreHow can we transfer information between MySQL and data files?
Transferring the information between MySQL and data files mean importing data from data files into our database or exporting data from our database into files. MySQL is having two statements that can be used to import or export data between MySQL and data files −LOAD DATA INFILEThis statement is used for importing the data from data files into our database. It reads data records directly from a file and inserts them into a table. Its syntax would be as follows −SyntaxLOAD DATA LOCAL INFILE '[path/][file_name]' INTO TABLE [table_name ];Here, the path is the address of the file.file_name is the name ...
Read MoreWhat is the maximum length of data we can put in a TEXT column in MySQL?
As we know TEXT data objects are useful for storing long-form text strings. The different TEXT objects offer a range of storage space from 255 bytes to 4 Gb. The following table shows the storage of different kinds of TEXT data type −Type of BLOBMaximum amount of Data that can be storedOverheadTINYTEXTUp to 255 bytes1 byteTEXTUp to 64 Kb2 bytes MEDIUMTEXTUp to 16 Mb3 bytesLONGTEXTUp to 4 Gb4 bytes
Read MoreOn inserting 'NULL', '0' or No Value to the column, will MySQL assign sequence number for AUTO_INCREMENT column?
MySQL will automatically assign sequence numbers to the AUTO_INCREMENT column even if we insert NULL, 0 or No Value to the column in a table.Examplemysql> create table test123(id INT PRIMARY KEY NOT NULL AUTO_INCREMENT, Name Varchar(10)); Query OK, 0 rows affected (0.15 sec)The query above created a MySQL table named ‘test123’ with columns named ‘id’ and ‘Name’. The column ‘id’ is declared AUTO_INCREMENT. Now, if we insert ‘No Value’, ‘0’ or ‘NULL’ in the ‘Name’ column, MySQL will assign the sequence numbers to column ‘id’. It can be seen from the result queries below −mysql> Insert Into test123(Name) values(''), ('0'), ...
Read MoreHow multiple inheritance is implemented using interfaces in Java?
Java does not support multiple inheritance. This means that a class cannot extend more than one class. Therefore, following is illegal −Examplepublic class extends Animal, Mammal{}However, a class can implement one or more interfaces, which has helped Java get rid of the impossibility of multiple inheritance.The extends keyword is used once, and the parent interfaces are declared in a comma-separated list.For example, if the Hockey interface extended both Sports and Event, it would be declared as −Examplepublic interface Hockey extends Sports, Event
Read MoreHow can I clear or empty a StringBuilder in Java.
You can either setLength to be 0 or create a new StringBuilder() instance. See the example below −Examplepublic class Tester { public static void main(String[] args) { StringBuilder builder = new StringBuilder(); builder.append("sample"); System.out.println(builder.toString()); builder.setLength(0); System.out.println(builder.toString()); builder.append("sample"); System.out.println(builder.toString()); } }Outputsample sample
Read MoreHow to install JDK in Windows and set up the environment variables?
Download the latest version of Java from the official site. Run the .exe to install Java on your machine. Once you installed Java on your machine, you will need to set environment variables to point to correct installation directories −Setting Up the Path for Windows:Assuming you have installed Java in c:\Program Files\java\jdk directory − Right-click on 'My Computer' and select 'Properties'.Click the 'Environment variables' button under the 'Advanced' tab.Now, alter the 'Path' variable so that it also contains the path to the Java executable. Example, if the path is currently set to 'C:\WINDOWS\SYSTEM32', then change your path to read 'C:\WINDOWS\SYSTEM32;c:\Program Files\java\jdk\bin'.
Read MoreHow can we return to windows command shell from MySQL command line tool?
The EXIT or QUIT commands take you returned to windows from MySQL command line tool.mysql> EXITORmysql> QUIT
Read MoreHow can we write MySQL query for inner joins with the help of Comma operator?
Writing inner joins with the help of comma operator is the most basic way to combine two tables. As we know that we can also write inner join by using keyword INNER JOIN or synonyms like JOIN. To form an inner join we need to specify a particular condition which is known as join-predicate and while writing inner joins using the comma operator, we use WHERE clause, the only way, to specify the join condition. To understand it, we are taking the example of two tables named tbl_1 and tbl_2 which are having following data:mysql> Select * from tbl_1; +----+--------+ ...
Read MoreWhat MySQL returns if I write only one value in the enclosed set of unit values for compound INTERVAL unit?
In this case, MySQL will take into consideration right most unit given in compound INTERVAL unit. It will return the output after calculating the interval on the basis of single value provided in the enclosed set of unit values. The following example will clarify it −mysql> Select TIMESTAMP('2017-10-22 04:05:36' + INTERVAL '2 ' year_month) AS 'Only Month Value Changed'; +--------------------------+ | Only Month Value Changed | +--------------------------+ | 2017-12-22 04:05:36 | +--------------------------+ 1 row in set (0.00 sec)The query above changes the month (right most in compound INTERVAL unit) from 10 to 12 based on the single value ...
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