Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
MySQL Articles
Page 6 of 355
How to select last 10 rows from MySQL?
To select last 10 rows from MySQL, we can use a subquery with SELECT statement and Limit concept. The following is an example. Creating a table. mysql> create table Last10RecordsDemo -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.75 sec) Inserting records into the table. mysql> insert into Last10RecordsDemo values(1, 'John'), (2, 'Carol'), (3, 'Bob'), (4, 'Sam'), (5, 'David'), (6, 'Taylor'); Query OK, 6 rows affected (0.12 sec) Records: 6 Duplicates: 0 Warnings: 0 mysql> insert into Last10RecordsDemo ...
Read MoreHow to cast from VARCHAR to INT in MySQL?
To cast VARCHAR to INT, we can use the cast() function from MySQL. Here is the syntax of cast() function. cast(anyValue as dataType) For our example, we will create a table with the help of CREATE command. mysql> create table VarchartointDemo -> ( -> Value varchar(100) -> ); Query OK, 0 rows affected (0.51 sec) After creating a table, let us insert some records into the table with the help of INSERT command. The query is as follows − mysql> insert into VarchartointDemo values('123'); Query OK, 1 row affected (0.26 sec) ...
Read MoreBest way to test if a row exists in a MySQL table
To test whether a row exists in a MySQL table or not, use exists condition. The exists condition can be used with subquery. It returns true when row exists in the table, otherwise false is returned. True is represented in the form of 1 and false is represented as 0.For better understanding, firstly we will create a table with the help of CREATE command. The following is the query to create a table −mysql> CREATE table ExistsRowDemo -> ( -> ExistId int, -> Name varchar(100) -> ); Query OK, 0 rows affected (0.53 sec)After creating the table successfully, we will ...
Read MoreTypes of dependencies in DBMS
Dependencies in DBMS is a relation between two or more attributes. It has the following types in DBMS −Functional DependencyFully-Functional DependencyTransitive DependencyMultivalued DependencyPartial DependencyLet us start with Functional Dependency −Functional DependencyIf the information stored in a table can uniquely determine another information in the same table, then it is called Functional Dependency. Consider it as an association between two attributes of the same relation.If P functionally determines Q, thenP -> QLet us see an example −EmpIDEmpNameEmpAgeE01Amit28E02Rohit31In the above table, EmpName is functionally dependent on EmpID because EmpName can take only one value for the given value of EmpID:EmpID -> EmpNameThe same is displayed ...
Read MoreHow to select first 10 elements from a MySQL database?
To select first 10 elements from a database using SQL ORDER BY clause with LIMIT 10.The syntax is as followsSELECT *FROM yourTableName ORDER BY yourIdColumnName LIMIT 10;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table Clients - > ( - > Client_Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > ClientName varchar(20) - > ); Query OK, 0 rows affected (0.51 sec)Insert some records in the table using INSERT command.The query is as followsmysql> insert into Clients(ClientName) values('Larry'); Query OK, 1 row affected (0.09 ...
Read MorePartial Dependency in DBMS
What is Partial Dependency?Partial Dependency occurs when a non-prime attribute is functionally dependent on part of a candidate key.The 2nd Normal Form (2NF) eliminates the Partial Dependency.Let us see an example −ExampleStudentIDProjectNoStudentNameProjectNameS01199KatieGeo LocationS02120OllieCluster ExplorationIn the above table, we have partial dependency; let us see how −The prime key attributes are StudentID and ProjectNo, andStudentID = Unique ID of the studentStudentName = Name of the studentProjectNo = Unique ID of the projectProjectName = Name of the projectAs stated, the non-prime attributes i.e. StudentName and ProjectName should be functionally dependent on part of a candidate key, to be Partial Dependent.The StudentName can be determined by StudentID, which makes the relation ...
Read MoreHow to select last row in MySQL?
To select the last row, we can use ORDER BY clause with desc (descending) property and Limit 1. Let us first create a table and insert some records with the help of INSERT command. The query is as follows. mysql> create table getLastRecord -> ( -> Id int, -> Name varchar(100) -> ); Query OK, 0 rows affected (0.61 sec) After creating the above table, we will insert records with the help of INSERT command. mysql> insert into getLastRecord values(1, 'John'); Query OK, 1 row affected (0.13 sec) ...
Read MoreHow to get the datatype of MySQL table columns?
You can get the MySQL table columns data type with the help of "information_schema.columns".The syntax is as follows −SELECT DATA_TYPE from INFORMATION_SCHEMA.COLUMNS where table_schema = 'yourDatabaseName' and table_name = 'yourTableName'To understand the above syntax, let us first create a table −mysql> create table DataTypeDemo −> ( −> Id int, −> Address varchar(200), −> Money decimal(10, 4) −> ); Query OK, 0 rows affected (0.60 sec)Apply the above syntax to get the MySQL columns data type. The query is as follows −mysql> select data_type from information_schema.columns where table_schema = 'business' and able_name = 'DataTypeDemo';The following is the output ...
Read MoreStarting 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 More