Dynamic Database Switching: Difference between revisions
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For some kinds of system - typically those which provide the same service to a number of different customer organisations - there may be a need to maintain multiple versions of ''some'' of the database tables, held within the same database server instance. | For some kinds of system - typically those which provide the same service to a number of different customer organisations - there may be a need to maintain multiple versions of ''some'' of the database tables, held within the same database server instance. | ||
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===The Database Switching Object=== | ===The Database Switching Object=== | ||
< | <source lang="vdf"> | ||
Use MerTech.inc | Use MerTech.inc | ||
Define C_InitialDB for "defaultDB" // This will be used for the tables to be | Define C_InitialDB for "defaultDB" // This will be used for the tables to be | ||
// initially opened in and for global tables | // initially opened in and for global tables | ||
// We define a global handle for the object which will handle the switching. | // We define a global handle for the object which will handle the switching. | ||
// We do this conditionally in case something else (see below) also defines it. | // We do this conditionally in case something else (see below) also defines it. | ||
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Global_Variable Handle ghoDbSwitch | Global_Variable Handle ghoDbSwitch | ||
#ENDIF | #ENDIF | ||
// We use the special Mertech command "Set_Database_Name" to establish the default | // We use the special Mertech command "Set_Database_Name" to establish the default | ||
// database as the one to initially open tables in: | // database as the one to initially open tables in: | ||
Set_Database_Name to C_InitialDB | Set_Database_Name to C_InitialDB | ||
// Define the class we are going to make an object of. This *could* be done | // Define the class we are going to make an object of. This *could* be done | ||
// directly in the object, but this way is "cleaner". | // directly in the object, but this way is "cleaner". | ||
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Function_Return sDB | Function_Return sDB | ||
End_Function // psCurrentDatabase | End_Function // psCurrentDatabase | ||
// Opens the "customer" tables | // Opens the "customer" tables | ||
Procedure OpenCustomerTables | Procedure OpenCustomerTables | ||
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Set_Database_Name to sDB | Set_Database_Name to sDB | ||
Send OpenCustomerTables | Send OpenCustomerTables | ||
End_Procedure | End_Procedure | ||
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End_Class // cDbSwitcher | End_Class // cDbSwitcher | ||
// Create an instance of the class: | // Create an instance of the class: | ||
Object oDbSwitcher is a cDbSwitcher | Object oDbSwitcher is a cDbSwitcher | ||
End_Object // oDbSwitcher | End_Object // oDbSwitcher | ||
</ | </source> | ||
