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There are many times that you will want to view, process, or report a sub-set of records from a file. There are two ways to do this:
1.Range Limit
2.Filters
Each method has its tradeoffs. Range Limits are much faster to process, but they require that a procedure or control use a limited key as the primary key. Filters are more flexible, since they don't require any special key manipulation, but they are much slower. In any procedure that does sequential processing, you can specify a Range Limit Field, and the type of Range Limit you want to use. The types provided are:
Current Value -Value Limited Keyed Access
The key element specified in the Range Limit Field prompt is the final Fixed Key Element. With this kind of Range Limit, the value of all Fixed Key Elements are saved when the procedure is initialized. These values are used for the duration of the procedure.
Single Value-Value Limited Keyed Access
The key element specified in the Range Limit Field prompt is the final Fixed Key Element. With this kind of Range Limit, the values of all Fixed Key Elements EXCEPT the final Fixed Key Element are saved when the procedure is initialized. The final Fixed Key Element is assigned the value specified in the Range Limit value prompt. This value can be either a variable or fixed value. This value is reevaluated each time a page or entry is loaded or processed.
Range of Values -Ranged Key Access
The key element specified in the Range Limit Field prompt is the first Free Key Element. With this kind of Range Limit, the values of all Fixed Key Elements except the final Fixed Key Element are saved when the procedure is initialized. The Low Limit and High Limit Values are used to set the keys for sequential access and to evaluate each record read to insure it is within the valid range. These values can be either fixed values or variables. If variables are used, these variables are reevaluated each time a page or entry is loaded or processed.
There is also support in this dialog for the Higher Key Component, which allows you to specify a secondary key component for Single Values and Range of Values, and then prime the higher component values accordingly.
Browse Box Only - File Relationship - Value Limited Key Access
All Fixed Key Elements are assigned values as defined in a relationship in the data dictionary. With this kind of Range Limit, it is possible to have multiple Browse Box control templates populated on a window, and as long as the relationships are defined and used, when a parent Browse Box goes out of range, all children (and grandchildren, etc.) Browse Boxes and Controls will automatically be reconstructed.
You must BIND any variables or EQUATEs used in a filter expression. Add the variable to the Hot Fields list, and check the Bind Field box.