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MySQLi Articles
Page 5 of 341
Best 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 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 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 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 MoreHow To Optimize MySQL Tables?
Optimizing MySQL tables is a crucial step in improving the performance and efficiency of your database. By employing effective optimization techniques, you can enhance query execution speed, reduce storage requirements, and optimize resource utilization. This article explores various strategies and best practices to optimize MySQL tables, allowing you to maximize the performance of your database-driven applications. In this guide, we will discuss the importance of analyzing table structure and design, selecting appropriate data types, and normalizing the database schema. We will also delve into indexing strategies, including identifying indexing opportunities and optimizing indexes for query performance. Additionally, we will explore ...
Read MoreHow to format number to 2 decimal places in MySQL?
You can use TRUNCATE() function from MySQL to format number to 2 decimal places. The syntax is as follows −SELECT TRUNCATE(yourColumnName, 2) as anyVariableName from yourTableName;To understand the above syntax, let us first create a table. The query to create a table is as follows −mysql> create table FormatNumberTwoDecimalPlace -> ( -> Number float -> ); Query OK, 0 rows affected (0.59 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into FormatNumberTwoDecimalPlace values(123.456); Query OK, 1 row affected (0.13 sec) mysql> insert into FormatNumberTwoDecimalPlace values(1.6789); Query OK, 1 ...
Read MoreDifference between localhost and 127.0.0.1?
On almost every machine, the localhost and 127.0.0.1 are functionally the same. But, they are not exactly the same. This article is meant for explain the important differences between localhost and 127.0.01. What is Localhost? "localhost" is the machine name or IP address of the host server. You can think of it as the domain name for "127.0.0.1". The localhost allows a network connection to loop back on itself. It is a communication port that is connected to the local server. It helps us in spoofing the network connections when such a network does not exist. We tend to use ...
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