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filereference:dbssystem [2020/10/26 21:32] – enviadmin | filereference:dbssystem [2021/07/26 21:06] – enviadmin |
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===== Database Design ===== | ===== Database Design ===== |
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[{{ :filereference:dbdesign_small.png?nolink 600 |Design of the ENVI-met database system in V4}}] | [{{ :filereference:dbdesign_small.png?nolink 600 |Design of the ENVI-met database system}}] |
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Each ENVI-met database, System or User/Project, holds the following tables: | Each ENVI-met database, System or User/Project, holds the following tables: |
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. |
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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. |
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[{{ :filereference:dblogic_small.png?nolink 500 |Logic of merging database items}}] | {{ :filereference:dblogic_small.png?nolink 500 |Logic of merging database items}} |
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