This directory contains the database schema required for
running the difxdb infrastructure.

1) Database versioning and file naming rules

The database schema is organized with a version number of the
form <major.minor>. The name of the files in this directory
should always reflect the version number the particular file
is asociated with. Also the schema file can contain
the full schema definition or only the updates from the last version
number. This is also reflected by the file name. Filenames containing
the word "full" have the full schema definition, wherease file names
containing "update" will only update the existing schema to the new version
number.
Note: The dixdb suite of programs can in principle 
be operated with various database servers, e.g. MySQL, PostGreSQL,
Oracle etc. However, the different architectures use slightly
different schema defintions. Therefore the filenames also should make
clear for which database server the schema defintion is intended.

Example:

difxdb_mysql_full_1_0.sql: Full schema definition of version 1.0 with MySQL specfic definitions

difxdb_oracle_update_1.1.sql. Update schema defition for version 1.1 with oracle specific definitions


2) Importing the schema

The schema needs to be imported into the database server.
To import the schema into a MySQL server run the following command:

mysql -h <dbserver> -u <dbuser> -p < difxdb_mysql_full_1_0.sql

This will import the the full schema version 1.0.

Beware: Importing the full schema will ALWAYS DROP all tables
already existing in the database consequently leading to loss of 
all data stored within. Before importing full schema defintions
you should always make a backup of the existing database.
Importing schema updates will leave existing tables/data untouched.

In order to update your schema to the highest version ALL update
files with version numbers higher than your current one need to be 
imported.

3) Adding new files to this directory

When adding new files to this directory always follow
the naming scheme described above:
difxdb_<architecture>_<full|update>_major_minor.sql

All files should set the version number (which is stored in 
table VersionHistory) at the end of the SQL script:

INSERT INTO `difxdb`.`VersionHistory` (
`major` ,
`minor`
)
VALUES (
'1', '1'
);

As a rule the major revision number should be increased whenever the changes in the schema introduce incompatibilities with previous versions (e.g. by dropping fields, changing the field types etc.). Changes that extend the schema (e.g. by adding tables or fields to existing tables) should increase the minor version number only.