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filereference:dbssystem [2020/10/26 21:31] – [Introduction] enviadminfilereference:dbssystem [2020/10/26 21:34] – [System Database and User/Project Database: Basic Concept] enviadmin
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 To link the information stored in the Area input files with the different database information, ENVI-met uses a [[wp> relational database]]:   To link the information stored in the Area input files with the different database information, ENVI-met uses a [[wp> relational database]]:  
-Each database entry is defined by a unique key, which has to be a **six-sign alphanumerical ID** in ENVI-met (e.g. '0000a0''"). Any reference to a database entry, may it be in an Area Input file or some other table of the database  is given by using this ID. For example, if you have defined a plant "''0000a0''" in your plant database, you can place it on a grid by setting the ID "''0000a0''" to this grid point. +Each database entry is defined by a unique key, which has to be a **six-sign alphanumerical ID** in ENVI-met. Any reference to a database entry, may it be in an Area Input file or some other table of the database  is given by using this ID. For example, if you have defined a plant "''0000a0''" in your plant database, you can place it on a grid by setting the ID "''0000a0''" to this grid point. 
  
 The ENVI-met database system is a global system which is used for each simulation and all ENVI-met applications.  The ENVI-met database system is a global system which is used for each simulation and all ENVI-met applications. 
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 If they all use different IDs, the resulting set will be simply the sum of the items in both databases with all items available. However, if you use the same ID for items in both the System DB and the User/Project DB, the user content in the User/Project DB will overwriten the System DB item.  If they all use different IDs, the resulting set will be simply the sum of the items in both databases with all items available. However, if you use the same ID for items in both the System DB and the User/Project DB, the user content in the User/Project DB will overwriten the System DB item. 
  
-In the example below, the System DB introduces 3 elements: ''AA'', ''BB'' and ''CC''. In the User DB, the elements ''BB'' and ''DD'' are defined (here in red to mark their orign).  The final result of elements will be ''AA'', ''BB'', ''CC'' and ''DD'' in which ''BB'' and ''DD'' are the items defined in the User DB. The item ''BB'' in the System DB will be overwritten and is not available until the item of the same ID will be removed from the User DB.+In the example below, the System DB introduces 3 elements: ''0000AA'', ''0000BB'' and ''0000CC'' (Let's skip the first four signs for readability). In the User DB, the elements ''BB'' and ''DD'' are defined (here in red to mark their orign).  The final result of elements will be ''AA'', ''BB'', ''CC'' and ''DD'' in which ''BB'' and ''DD'' are the items defined in the User DB. The item ''BB'' in the System DB will be overwritten and is not available until the item of the same ID will be removed from the User DB.
  
-[{{ :filereference:dblogic_small.png?nolink 500 |Logic of merging database items}}+{{ :filereference:dblogic_small.png?nolink 500 |Logic of merging database items}}