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Database Articles
Page 131 of 547
Starting and Stopping MySQL Server
Let us understand how MySQL server can be started and stopped on Linux and Windows −Linux – Start and Stop ServerOn Linux, the start and stop can be done from the command line as shown below −/etc/init.d/mysqld start /etc/init.d/mysqld stop/etc/init.d/mysqld restartLinux – Service CommandsSome Linux types offer service command as well −service mysqld startservice mysqld stop service mysqld restart(or)service mysql startservice mysql stopservice mysql restart Windows – Start and Stop ServerLet us understand how it can be done on Windows −Open 'Run' Window by using Win key + RType 'services.msc'Now search for MySQL service based on the version that ...
Read MoreHow to create a table with date column?
To create a table with only date column, you can use DATE type. Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(20), StudentAdmissionDate DATE ); Query OK, 0 rows affected (0.47 sec)Insert records in the table using INSERT command −mysql> insert into DemoTable(StudentName, StudentAdmissionDate) values('Chris', now()); Query OK, 1 row affected, 1 warning (0.12 sec) mysql> insert into DemoTable(StudentName, StudentAdmissionDate) values('Robert', curdate()); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(StudentName, StudentAdmissionDate) values('David', '2019-05-21'); Query OK, 1 row affected (0.16 sec)Display all ...
Read MoreHow do I show the schema of a table in a MySQL database?
To show the schema, we can use the DESC command. This gives the description about the table structure. The following is the syntax. DESCRIBE yourDatabasename.yourTableName; Let us implement the above syntax. mysql> DESCRIBE business.student; The following is the output. +-------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+--------------+------+-----+---------+-------+ | id | int(11) | YES | MUL | NULL | | | Name | varchar(100) | YES | MUL | NULL | | +-------+--------------+------+-----+---------+-------+ 2 rows in set (0.05 ...
Read MoreDDL(Data definition language)
Data Definition Language(DDL) is used for describing data and its relationship in a database. It is also used to define the database schema. The commands only affect the database structure and not the data. The main DDL commands are create, alter, drop and truncate. Create Statement It is used to create a database or table. While creating the table, we specify table_name, column_name followed by data_types(int, float, varchar, etc) and constraints(primary key, not null, etc) Syntax CREATE TABLE table_name ( column1 datatype, column2 datatype, ..... ) Example In this ...
Read MoreData Control Language(DCL)
DCL(Data Control Language) work is to deal with sql commands that are used to permit a user to access, modify and work on a database. it is used to access stored data. It gives access, revoke access and change the permission to the owner of the database as per the requirement. It helps in how sql can use a user authority to modify or retrieve data and protect against unauthorised access. It complements data manipulation language(DML) and data definition language(DDL). It is the simplest among the three command It is basically used for enforcing data security. DCL Commands ...
Read MoreData Replication
Data replication means copying the data at multiple locations to improve the availability of data. It is used to remove the inconsistency between the same data which results in a distributed database so that users can do their own task without interrupting the work of other users. There are various types of Data Replication in DBMS as follow − Types of Data Replication Transactional Replication It makes a full copy of the database along with the changed data. Transactional consistency is guaranteed because the order of data is the same when copied from publisher to subscriber database. It is ...
Read MoreData Preprocessing in Data Mining
Data preprocessing is an important process of data mining. In this process, raw data is converted into an understandable format and made ready for further analysis. The motive is to improve data quality and make it up to mark for specific tasks. Tasks in Data Preprocessing Data cleaning Data cleaning help us remove inaccurate, incomplete and incorrect data from the dataset. Some techniques used in data cleaning are − Handling missing values This type of scenario occurs when some data is missing. Standard values can be used to fill up the missing values in a manual way but ...
Read MoreData Objects, Attributes and Relationship in DBMS
Data Objects Data objects refers to a collection of various attributes which are combined to make it understandable. Data object values have their own unique id, attribute and data types. The most common type is the data table. Data objects are mostly represented in data models, which resolve with the relationship among the data objects. Types of Data Objects Array is a one-dimension data object. i.e, can be a single column in a table. Example Student Name Aman Naman Monu Records Records refers to a single row for every ...
Read MoreData Modeling for Data Warehouse
Data modeling refers to the process of handling and designing the data model within a data warehouse platform. It consists of making an appropriate database schema so as to transfer the data that can be stored and of useful to user. Data warehouse modeling is used for two reasons, first is that relationship within the warehouse data can be visualised through the schema and second is that the cost is reduced and efficiency is increased with the help of well-designed schema which allow effective data warehouse structure to occur. Data modeling is different in data warehouse than in operational database ...
Read MoreData Mining:Data Attributes and Quality
Data Mining The process of extracting the data from a huge dataset that can be used for analysis and benefit of the organisation. This process helps in identifying patterns and managing relationship among the data to predict business problems. Data attributes An attribute can be defined as characteristics or property of an object. Object is described by attributes set and is referred to as a record of entity. Entity is described by a fraction of data i.e. attributes. For Example:In a Student database. (Name, id, Roll_no, Marks) are the attributes in provided database. Types of Attributes Nominal Attribute It only ...
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