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Articles by Jennifer Nicholas
Page 9 of 21
What is the use of CHECK TABLE statement in maintaining the MySQL tables?
There may be something wrong which can happen to the database server e.g., the server was shutdown unexpectedly, error while writing data to the hard disk, etc. These situations could make the database operate incorrectly and in the worst case, it can be crashed.With the help of CHECK TABLE statement MySQL allows us to check the integrity of database tables. Its syntax would be as follows −CHECK TABLE table_nameHere, table_name is the name of the table.ExampleWe are running this statement for the table Student_info as follows −mysql> CHECK table student_info\G *************************** 1. row *************************** Table: query.student_info ...
Read MoreHow DIFFERENCES between tables can be implemented with the help of MySQL joins?
We can get the differences between the tables by unioning exclusion joins from 1st table to 2nd table and from 2nd table to 1st table. To understand it, we are taking the example of following two tables −mysql> Select * from value1; +-----+-----+ | i | j | +-----+-----+ | 1 | 1 | | 2 | 2 | +-----+-----+ 2 rows in set (0.00 sec) mysql> Select * from value2; +------+------+ | i | j | +------+------+ | ...
Read MoreWhat would be the effect on the output of MySQL LAST_INSERT_ID() function in the case on multiple-row insert?
As we know that MySQL LAST_INSERT_ID() function returns the latest generated sequence number but in case of multiple row-insert it would return the sequence number generated by the foremost inserted row.Examplemysql> Insert into Student(Name) values('Ram'), ('Mohan'), ('Aryan'); Query OK, 3 rows affected (0.03 sec) Records: 3 Duplicates: 0 Warnings: 0The query above inserts three values in Student table with the help of Multiple-row insert query. The value of Column ‘Id’ can be checked with the help of the following query −mysql> Select * from Student; +----+-------+ | Id | Name | +----+-------+ | 1 | Raman | | 2 | ...
Read MoreHow can I store the fixed length string as well as variable length string in the same MySQL table?
As we know that CHAR is used to store fixed length string and VARCHAR is used to store variable length strings. Hence we can store a fixed length as well as variable length string in the same table by declaring a column as CHAR and other as VARCHAR.Examplemysql> Create Table Employees(FirstName CHAR(10), LastName VARCHAR(10)); Query OK, 0 rows affected (0.64 sec) mysql> Desc Employees; +-----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+-------------+------+-----+---------+-------+ | FirstName | char(10) | YES ...
Read MoreWhat are multiplicative operators in C++?
The multiplicative operators are −Multiplication (*)Division (/)Modulus or “remainder from division” (%)These binary operators have left-to-right associativity. The multiplicative operators take operands of arithmetic sorts. The modulus operator (%) contains a stricter requirement in this its operands should be of integral type.The multiplication operator yields the result of multiplying the first operand by the second.The division operator yields the result of dividing the first operand by the second.The modulus operator yields the remainder given by the subsequent expression, wherever e1 is that the 1st operand and e2 is that the second: e1 – (e1 / e2) * e2, where both ...
Read MoreHow can we take a backup of a particular table from a database by using mysqldump client program?
By using mysql dump client program we can take the backup of a particular table from the databases into a file having the extension ‘.sql’. It can be understood with the help of the following example −ExampleIn this example, with the help of mysql dump client program, we are taking the backup of a table named ‘student_info’ from ‘query’ database in a file named ‘student_info.sql’. The following command will do this:C:\mysql\bin>mysqldump -u root query student_info > student_info.sqlThe above command will create a file named student_info.sql which has the dump information of a file named ‘student_info’ from database named ‘query’.
Read MoreHow to get the total number of seconds from a MySQL DATETIME instance?
The MySQL DateTime instance can be converted into seconds with the help of UNIX_TIMESTAMP() function in the following way −mysql> Select UNIX_TIMESTAMP('2017-05-15 04:05:30') AS 'NUMBER OF SECONDS'; +-------------------+ | NUMBER OF SECONDS | +-------------------+ | 1494801330 | +-------------------+ 1 row in set (0.00 sec)Above query will convert the given datetime instance into total number of seconds.mysql> Select UNIX_TIMESTAMP(NOW()) AS 'NUMBER OF SECONDS'; +-------------------+ | NUMBER OF SECONDS | +-------------------+ | 1509248856 | +-------------------+ 1 row in set (0.00 sec)Above query will convert the current DateTime instance into a total number of seconds.mysql> ...
Read MoreWhat is the way to find business days between two specified dates in MySQL?
With the help of DATEDIFF(expr1, expr2) we can find the business days between two specified dates.For example, if we want to find business days between ‘2017-05-27’ and ‘2017-05-23’ then following would be MySQL query −mysql> Select DATEDIFF('2017-05-27','2017-05-23') AS 'Total Business Days'; +----------------------+ | Total Business Days | +----------------------+ | 4 | +----------------------+ 1 row in set (0.00 sec)
Read MoreHow to use singleton dialog in android?
Before getting into an example, we should know what singleton design pattern is. A singleton is a design pattern that restricts the instantiation of a class to only one instance. Notable uses include controlling concurrency and creating a central point of access for an application to access its data store.This example demonstrates How to use singleton dialog in androidStep 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. In the above ...
Read MoreHow to set/insert null values to in to a column of a row using JDBC program?
You can insert null values into a table in SQL in two ways:Directly inserting the value NULL into the desired column as:Insert into SampleTable values (NULL);Using ‘ ’ as nullInsert into SampleTable values (NULL);While inserting data into a table using prepared statement object you can set null values to a column using the setNull() method of the PreparedStatement interface.pstmt.setNull(parameterIndex, sqlType);ExampleAssume we have a table named cricketers_data in the database with the following contents:+------------+------------+---------------+----------------+-------------+ | First_Name | Last_Name | Date_Of_Birth | Place_Of_Birth | Country | +------------+------------+---------------+----------------+-------------+ | Shikhar | Dhawan | 1981-12-05 | ...
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