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MySQLi Articles
Page 6 of 341
Difference 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 ...
Read MorePriority of AND and OR operator in MySQL select query?
The AND has the highest priority than the OR operator in MySQL select query.Let us check how MySQL gives the highest priority to AND operator.The query is as followsmysql> select 0 AND 0 OR 1 as Result;The following is the output+--------+ | Result | +--------+ | 1 | +--------+ 1 row in set (0.00 sec)If you are considering the OR operator has the highest priority then MySQL will wrap up the above query like this.The query is as followsselect 0 AND (0 OR 1) as ResultFirst, solve the 0 OR 1, this will give result 1. After that ...
Read MoreDifference Between ALTER and UPDATE Command in SQL
In this post, we will understand the difference between the ALTER command and the UPDATE command in SQL.ALTER CommandThis command is a Data Definition Language (DDL).It performs operation at the structural level, not the data level.This command is used to add, delete, and modify the attributes of the tables in a database.This command, by default, initializes the values of all values in the tuple to NULL.It changes the structure of the table.Syntax: Add a column −ALTER TABLE table_name ADD column_name datatype;Drop a ColumnALTER TABLE table_name DROP COLUMN column_name;UPDATE CommandThis command is a Data Manipulation Language (DML).It performs operations on the ...
Read MoreWhat Is the Default MySQL Port Number?
MySQL uses port number 3306 by default.3306 Port Number3306 port number is used by MySQL protocol to connect with the MySQL clients and utilities such as ‘mysqldump’. It is a TCP, i.e Transmission Control Protocol.VulnerabilitiesLet us see if there are any vulnerabilities while using this default port −In general, port 3306 shouldn’t be opened since it could make the server vulnerable to attack. If the user needs to connect to the database remotely, there are many other secure options, instead of opening the port 3306.One of the secure options includes using an SSH tunnel. On the other hand, if it ...
Read MoreHow can I determine the connection method used by a MySQL Client?
To determine the connection method that is used by MySQL connection, the below command can be used −netstat −ln | grep 'mysql'On Unix, MySQL programs treat the host name ‘localhost’ in a special manner. Hence, it behaves differently than what is expected of it.Type of ConnectionTo know the type of connection from within the mysql CLI, the below command can be used −mysql> \sOutput −Connection: 127.0.0.1 via TCP/IP (or) Connection: Localhost via UNIX socketTCP/IP connection to the local serverTo ensure that the client makes a TCP/IP connection to the local server, the --host or -h can be used. This will ...
Read MoreMySQL Administrative and Utility Programs
Let us look at the administrative and utility programs in MySQL and understand how they can be used −ibd2sdiIt is a utility to extract serialized dictionary information (SDI) from InnoDB tablespace files. SDI data is present all persistent InnoDB tablespace files. ibd2sdi can be used at runtime or when the server is offline.innochecksumIt prints the checksums for InnoDB files. It reads an InnoDB tablespace file, calculates the checksum for every page, compares the calculated checksum to the stored checksum, and reports mismatches, which show the damaged pages. It was originally developed to speed up the verification of the integrity of ...
Read MoreDisplay MySQL Database, Table, and Column Information
The mysqlshow client can be used to see what databases exist, their tables, or a table's columns or indexes.It provides a command-line interface for several SQL SHOW statements.Invoke mysqlshowThe mysqlshow utility can be invoked as shown below −shell> mysqlshow [options] [db_name [tbl_name [col_name]]]Here, If no database is provided, a list of database names are displayed.If no table is given, all matching tables in the database are displayed.If no column is provided, all matching columns and column types in the table are shown.The output displays the names of only those databases, tables, or columns for which the user has certain privileges.Optionsmysqlshow ...
Read Moremysqlimport - A MySQL Data Import Program
The mysqlimport client comes with a command-line interface that helps with the LOAD DATA SQL statement. Most options to mysqlimport respond directly to clauses of LOAD DATA syntaxInvoking mysqlimportThe utility mysqlimport can be invoked as shown below −shell> mysqlimport [options] db_name textfile1 [textfile2 ...]For every text file that is named on the command line, mysqlimport strips any extension from the file name and uses the result to figure out the name of the table into which the file's contents have to be imported.ExampleLet us take an example: Files named sample.txt, sample.text, and sample all would be imported into a table ...
Read Moremysqldump - A MySQL Database Backup Program
The mysqldump client utility helps performs logical backups, thereby producing a set of SQL statements which can be executed to reproduce the original database object definitions and table data.mysqldump UsageIt dumps one or more MySQL databases for backup or transfer to another SQL server.The mysqldump command also generates output in CSV, other delimited text, or XML format.The utility mysqldump requires at least the SELECT privilege for dumped tables, SHOW VIEW for dumped views, TRIGGER for dumped triggers, LOCK TABLES if the --single-transaction option is not used, and PROCESS if --no-tablespaces option is not used.The databases can be cloned for the ...
Read Moremysqlcheck - A MySQL Table Maintenance Program
The mysqlcheck client performs table maintenance. It checks, repairs, optimizes, or analyses tables. If the user uses the --databases or --all-databases option to process all tables in one or more databases, invoking mysqlcheck would take a long time. This is true for the MySQL upgrade procedure as well, if it determines that the table checking is required since it processes tables in the same way.mysqlcheck UsageThe command mysqlcheck should be used when the mysqld server is running. This means that the user need not have to stop the server to perform table maintenance. It uses the SQL statements such as ...
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