CiviCRM Database Information¶
CiviCRM has a complex Database structure which this chapter will examine in more depth. CiviCRM for various reasons has the Schema structure of its database written out in XML files store in
xml/templates/schema These files are used to define all Core CiviCRM tables that are installed when CiviCRM is installed. CiviCRM maintains a number of tools and scripts such as
bin/regen.sh, the purpose of these tools is to update any current database with the lastest information stored in the XML files, Re-create the installation .mysql files that live in
sql/civicrm*.mysql which are not committed to the Git Repo but found in the downloadable package. Also They update the "DAO" Files which contain a reference of what files and what relationships are there in the database.
Documentation on tools to interact with the CiviCRM Database still to come.
Useful coding structures¶
Only full group by¶
When writing direct Database queries sometimes they can cause issues due to the sql mode
ONLY_FULL_GROUP_BY which aims to ensure that all columns in the group by / order by are in the select query and aggregated properly. If a query is particularly problematic that SQL mode can be temporarily disabled by putting a call in to
CRM_Core_DAO::disableFullGroupByMode() before the DB query function then
CRM_Core_DAO::reenableFullGroupByMode() immediately after. It is recommended that the original query is fixed rather than deploying this workaround however the workaround maybe the only real solution.