It is important to update joomla to the latest Joomla version. Depending on Joomla Version you have, after the update it can give database error. This is because the database is not up to date.
How to fix it follow the info below.
Login joomla backend.
Go in menu Extensions → Manage → Database. In there is any errors in your site, you will see a warning “Database is not up to dated” and a list of database problems.
On the upper left corner click on the icon titled Fix button. If the database issues are resolved, it will appear the notice “Database table structure is up to date”