Setting up foreign keys in phpMyAdmin?

If you want to use phpMyAdmin to set up relations, you have to do 2 things. First of all, you have to define an index on the foreign key column in the referring table (so foo_bar.foo_id, in your case). Then, go to relation view (in the referring table) and select the referred column (so in … Read more

When to use SELECT … FOR UPDATE?

The only portable way to achieve consistency between rooms and tags and making sure rooms are never returned after they had been deleted is locking them with SELECT FOR UPDATE. However in some systems locking is a side effect of concurrency control, and you achieve the same results without specifying FOR UPDATE explicitly. To solve this problem, Thread … Read more

#1055 – Expression of SELECT list is not in GROUP BY clause and contains nonaggregated column this is incompatible with sql_mode=only_full_group_by

I had a struggle getting this to work i’ve tested it and it’s working on lamp server mysql version 5.12 So, steps to success: sudo vim /etc/mysql/conf.d/mysql.cnf Scroll to the bottom of file Copy and paste[mysqld] sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION to the bottom of the file save and exit input mode sudo service mysql restart to restart MySQL. Done!

Authentication plugin ‘caching_sha2_password’ cannot be loaded

You can change the encryption of the user’s password by altering the user with below Alter command : ALTER USER ‘username’@’ip_address’ IDENTIFIED WITH mysql_native_password BY ‘password’; OR We can avoid this error by make it work with old password plugin: First change the authentication plugin in my.cnf file for Linux / my.ini file in Windows: [mysqld] … Read more

How to restart remote MySQL server running on Ubuntu linux?

SSH into the machine. Using the proper credentials and ip address, ssh [email protected]. This should provide you with shell access to the Ubuntu server. Restart the mySQL service. sudo service mysql restart should do the job. If your mySQL service is named something else like mysqld you may have to change the command accordingly or try this: sudo /etc/init.d/mysql restart

What is the definition of cardinality in SQL

They are speaking the same thing and it has to do with tuples (relational algebra) or rows (layman’s term). When it says high-cardinality are possible values of particular attribute (or field) that are unique and therefore the number of rows or tuples are higher: Example: As far as as StudentID the cardinality is high because it is unique. In this it … Read more

Mysql: Setup the format of DATETIME to ‘DD-MM-YYYY HH:MM:SS’ when creating a table

“MySQL retrieves and displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format.” This is from mysql site. You can store only this type, but you can use one of the many time format functions to change it, when you need to display it. Mysql Time and Date functions For example, one of those functions is the DATE_FORMAT, which … Read more