## 3 Results
### Structure of the Developed Databases  
As indicated in the previous section, the RDBMS has a common database and a series of individual databases corresponding to each PV installation analysed or each sector of them in the case of plants with a larger number of inverters. A schematic diagram of this RDBMS is shown in Figure 6.  
The main tables included in the developed common database are shown in Table 4. As previously mentioned, the information in some of these tables, such as the _Installations_, _Modules_ and _Inverters_ tables, must be filled in manually, and the information corresponding to some of them, such as the _Parameters_ and _Installation_Inverters_ tables, is filled in automatically when the data file migration process takes place. Figure 5: Schematic diagram representing the structure of the developed system for data analysis from PV plants. \begin{table}
\begin{tabular}{c c} \hline \hline
**Table Name** & **Description** \\ \hline \hline \begin{tabular}{c} _Spanish\_Municipalities\_and\_Provinces_ \\ _Installations_ \\ _Module\_Manufactures_ \\ _List of the modules commercialised by different \\ _Manufactures_, with their specifications: Material, \\ _Module\_ \\ _Module\_ \\ _Module\_ \\ \end{tabular}  & \ \begin{tabular}{c} To facilitate entering the location of the PV \\ installations to be analysed \\ _Installations_ \\ _Installations_ \\ _List of trade names of manufacturers of PV modules. \\ _List of the modules commercialised by different \\ _Manufactures_, with their specifications: Material, \\ _Number of cells_, Module surface, Nominal power of \\ _Module\_ \\ _(NOCT), Temperature coefficients, Open circuit \\ _voltage_, Short circuit current, Voltage and Current for \\ _maximum power_. \\ _Technical characteristics together with their \\ _Inverters_ \\ _Inverters_ \\ _monitored data are inserted into the RDBMS during \\ data migration._ \\ \end{tabular}  &
\begin{tabular}{c} _The RDBMS_ \\  
Several queries have been included in this common database, some of which are specifically prepared for the operation of the developed web application. One of them is called _Active_Installations_, which shows the list of PV installations for which data is stored in the databases and which will be accessible from the web application. Another important query is _Installation_Properties_, which shows a complete summary of the specifications of active installations. Another query worth mentioning is _InstallationMetering_Devices_, which generates a list of all the measuring devices that record the data in the different PV installations, with their identification codes, together with their characterisation, such as the associated modules, their nominal PV power, or the useful surface in m\({}^{2}\) of PV cells that modules connected to each monitoring device have. This is a query used by the web application to display all the information corresponding to the installation that has been selected by the user. It is also used to calculate parameters from the monitored data such as module or inverter efficiencies. The common database also includes a procedure called _Date_List_ in which, starting from two dates, you have the list of all the days between them. The individual databases dedicated to storing the monitoring data of each PV plant or one of its sections are composed of the tables shown in Table 5. The _Installation_Parameters_ table contains the list of parameters that are measured by each inverter. Its information facilitates the extraction of data from the database once they are already stored, since it allows the verification of whether a parameter is measured by an inverter, in order to proceed or not to export it. This is because not all inverters monitor the same parameters. The _ListofDays_ table contains the list of all the days for which data are available for that installation, from a minimum date or the oldest date for which data are available, to a maximum or most recent date. This table makes it easy to extract the values of each parameter, once stored, in the form of arrays.