Thursday, March 1, 2012

How to make a temporary instance of a database table to be shown on the form

This short code shows how to work with a temporary table without creating it in AOT.

// how to use temporary table
// method Init of the form
public void init()
    WmpInventNutrition        nut; // regular table in AOT
    WmpInventNutrition        tmp; // instead of creating in AOT a temporary table
                                   // we can create a temporary instance of the preivous regular table

    // here we make it temporary;
    // it will disappear from memory when loses the scope
    // in other words, when we close the form

    // simply selecting some of records from the regular table
    while select nut
        where nut.ItemId like '_wmp*'
        // and putting them in the temporary one;
    // finally to show them on the form
    // we set the form data source to the temporary table

Alternatively, if you know exactly how the field match, it will be faster to use insert_recordset:

 // simply selecting some of records from the regular table
    insert_recordSet tmp (itemid) select ItemId from nut where nut.ItemId like '_wmp*';

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