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- Automatic management of composite keys
- Filter and filtered iteration
- Enabling/Disabling a filter
- Non-HFSQL data files
HFilterIncludedBetween (Function) In french: HFiltreComprisEntre
 Not available with this kind of connection
Defines and enables an "Included between" filter on a data file, view or query. The "Included Between" filter is used to select all the records included between two values. After its execution, the most common cases are as follows: - the filter cannot be created: HFilterIncludedBetween returns an empty string (""). HError returns the error identifier.
- the filter is created: HFilterIncludedBetween returns the optimized search key that will be used to loop through the data file, view or query.
MySearchKey is string
MySearchKey = HFilterIncludedBetween(Customer, LastNameFirstName, ...
"A", "B" + hMaxVal, hBoundSeparator, "C", "D" + hMaxVal)
// Select all the customers whose last name is included between A and C
// and whose first name is included between C and D
HReadFirst(Customer, MySearchKey)
WHILE NOT HOut(Customer)
Trace(Customer.CustomerName, Customer.City)
HReadNext(Customer, MySearchKey)
END
...
// Disables the filter
HDeactivateFilter(Customer)
Syntax
<Result> = HFilterIncludedBetween(<Data file> , <Key item> , <Lower bound of key component 1> [, <Lower bound of key component N> [... [, <Lower bound of key component 2>]]] , <hBoundSeparator> , <Upper bound of key component 1> [, <Upper bound of key component 2> [... [, <Lower bound of key component 2>]]])
<Result>: Character string Browse item. Corresponds to:- the search key of data file if the filter is enabled.
- an empty string ("") if the filter cannot be implemented.
<Data file>: Character string Name of data file, view or query used. <Key item>: Character string Name of key item onto which the filter will be applied. This item can be a simple key (string) or a composite key.
Caution: this parameter must only contain letters, underlined characters or digits. Otherwise, the name must be enclosed in quotes. <Lower bound of key component 1>: Type of the first component of the search key Lower bound for the components (first, second, etc.) of the composite key. The records corresponding to this value will be included in the filter.
The type of this parameter must correspond to the type of key item component on which the filter is defined. <Lower bound of key component N>: Type of the second component of the search key Lower bound for the second component of the composite key. The records corresponding to this value will be included in the filter.
The type of this parameter must correspond to the type of key item component on which the filter is defined. <Lower bound of key component 2>: Type of nth component of search key Lower bound for the nth component of the composite key. The records corresponding to this value will be included in the filter.
The type of this parameter must correspond to the type of key item component on which the filter is defined. <hBoundSeparator>: Integer constant The hBoundSeparator constant is used to separate the values of lower and upper bounds for the components of the composite key. <Upper bound of key component 1>: Type of the first component of the search key Upper bound for the components (first, second, ...) of composite key. The records corresponding to this value will be included in the filter.
The type of this parameter must correspond to the type of key item component on which the filter is defined. <Upper bound of key component 2>: Type of the second component of the search key Upper bound for the second component of the composite key. The records corresponding to this value will be included in the filter.
The type of this parameter must correspond to the type of key item component on which the filter is defined. <Lower bound of key component 2>: Type of nth component of search key Lower bound for the nth component of the composite key. The records corresponding to this value will be included in the filter.
The type of this parameter must correspond to the type of key item component on which the filter is defined. Remarks Automatic management of composite keys HFilterIncludedBetween automatically manages the filters on the simple keys and on the composite keys. Example: Using HFilterIncludedBetween with a simple key:
ResultFilter = HFilterIncludedBetween(Customer, LastName, "A", hBoundSeparator, "B" + hMaxVal)
// Select all the customers whose last name is included between A and C
Example: Using HFilterIncludedBetween with a composite key
ResultFilter = HFilterIncludedBetween(Customer, LastNameFirstName, "A", "B" + hMaxVal, ...
hBoundSeparator, "C", "D" + hMaxVal)
// Select all the customers whose last name is included between A and C
// and whose first name is included between C and D
This line of code is equivalent to:
HFilter(Customer, LastNameFirstName, ...
HBuildKeyValue(Customer, LastNameFirstName, "A", "B" + hMinVal), ...
HBuildKeyValue(Customer, LastNameFirstName, "C", "D" + hMaxVal))
Filter and filtered iteration After the call to HFilterIncludedBetween, the iteration must be performed on the item returned by HFilterIncludedBetween. The filter will be ignored if another item is used to loop through the data file. When a filter is defined and enabled on a data file (view or query), all records read correspond to the filter. If no other record corresponds to the filter during the iteration: - HOut returns True.
- the current record corresponds to the last record read with the filter.
For example: | | | On a filtered data file, after the function: | the current record is: | | HReadFirst | the first file record corresponding to the filter | | HReadLast | the last file record corresponding to the filter | | HReadNext (or HForward) | the next record (or the next nth record) corresponding to the filter | | HReadPrevious (or HBackward) | the previous record (or the previous nth record) corresponding to the filter |
Enabling/Disabling a filter - HDeactivateFilter is used to disable a filter.
- HActivateFilter is used to re-enable a filter.
- The filter is deleted when the data file (query or view) is closed (HClose for example).
- A single filter can exist at a given time on a data file (query or view). If HFilterIncludedBetween is used several times, only the last filter will be taken into account: the previous filters will be deleted. Similarly, if several filters are used (HFilter* functions), only the last filter will be taken into account.
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