UNIQUE Constraint The UNIQUE constraint ensures that all values in a column are different. Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint. However, you can have many UNIQUE constraints per table, but only one PRIMARY KEY constraint per table. This constraint ensures that all values inserted into the column … Read more
NOT NULL Constraint By default, a column can hold NULL values. The “NOT NULL constraint” enforces a column to NOT accept NULL values. This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field. This constraint specifies that … Read more
MySQL Constraints SQL constraints are used to specify rules for data in a table. The constraint in MySQL is used to specify the rule that allows or restricts what values or data will be stored in the table. They provide a suitable method to ensure data accuracy and integrity inside the table. It also helps … Read more
MySQL CREATE TABLE Statement The MySQL CREATE TABLE Statement The CREATE TABLE statement is used to create a new table in a database. Syntax CREATE TABLE table_name ( column1 datatype, column2 datatype, column3 datatype, …. ); The column parameters specify the names of the columns of the table. The datatype parameter specifies the type of data the … Read more
MySQL AUTO INCREMENT Field What is an AUTO INCREMENT Field? Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table. Often this is the primary key field that we would like to be created automatically every time a new record is inserted. MySQL AUTO_INCREMENT Keyword MySQL uses … Read more
Install MySQL / MariaDB Server with PhpMyAdmin Centos 8 Install PHP, MySQL support package for PHP, and other PHP packages on your system for phpMyAdmin to connect with the database. dnf install -y wget php php-pdo php-pecl-zip php-json php-common php-fpm php-mbstring php-cli php-mysqlnd php-xml tar Install below PHP packages for phpMyAdmin to connect with the … Read more
MySQL is dead but subsys locked Issue Description: When tried to connect to MySQL or run any command. It Displayed The Following Error: Can’t connect to local MySQL server through socket ‘/var/mysql/mysql.sock'(2) When checked the status of MySQL service from the below command: service mysqld status as a root user I got : mysql is dead … Read more
How to check table Engine in MySQL With the help of below query, we can check the table engine in MySQL: SELECT TABLE_NAME, ENGINE FROM information_schema.TABLES WHERE TABLE_SCHEMA = ‘nicesys’; Please change the db name to your DB name. You will get the output like : | TABLE_NAME | ENGINE | +——————–+——–+ | cdr | … Read more
MySQL Addtime() : Adding time to datetime The ADDTIME() function adds a time interval to a time/datetime and then returns the time/datetime. Syntax ADDTIME(datetime, addtime) Parameter Values Parameter Description datetime Required. The time/datetime to be modified addtime Required. The time interval to add to datetime. Both positive and negative values are allowed Example: SELECT ADDTIME(“2021-06-03 09:34:21”, “2”); Output: … Read more
SQL language also includes syntax to update, insert, and delete records. These query and update commands together form the Data Manipulation Language (DML) part of SQL: • INSERT INTO – inserts new data into a database table • UPDATE – updates data in a database table • DELETE – deletes data from a database table … Read more