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Multi-Purpose Forms

Overview

These are called multi-purpose forms because they allow several functions (e.g. SELECT, LIST, ADD, MODIFY and DELETE) to be performed in a single component rather than having a separate component for each function.

There are several reasons why this type of component may be chosen:-

• Where a database table has few fields and the table contents are fairly static and can only be changed by someone with high security clearance (eg: the System Supervisor). In this case having separate forms to add, delete and modify would seem to be an overkill. The general user will only be able to view the contents of this table through a separate read-only function (eg: a popup). This type of component is often referred to as static data maintenance. Refer to MULTI 1, MULTI 2 and MULTI 3.

• Where a database table exists just to indicate whether there is a link between two other tables, as in a ONE-to-MANY-to-ONE relationship. In this situation the existence of an occurrence of MANY indicates that a link between the two other tables does exist, and the absence of an occurrence indicates that a link does not exist. In these circumstances the provision of separate components for LIST, ADD and DELETE would be too cumbersome for the user to handle. Refer to MULTI 4 and MULTI 5.

Multi 1 - Maintain occurrences, multiple occurrence display

Description

This type of form is for those entities where the number of fields is so small that each occurrence can be displayed on a single line. Two fields are shown in this example, but there may be more.

Upon initial entry the form will perform an automatic retrieve of all available entries, therefore may not be suitable for a table with large volumes of data.

The user makes whatever modifications are required, then preses the OK button to update the database, terminate and return control to the previous form.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 2 - Maintain occurrences, single occurrence display

Description

This type of form is for those occasions where the contents of each occurrence is too large to fit into a single line, therefore the screen can only show one occurrence at a time.

Upon initial entry the form will perform an automatic retrieve of all available entries, therefore may not be suitable for a table with large volumes of data.

The user makes whatever modifications are required, then preses the OK button to update the database, terminate and return control to the previous form.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 3 - Maintain MANY in a ONE-to-MANY relationship

Description

This type of form is used in a ONE-to-MANY relationship in order to maintain the occurrences of the MANY entity for a selected occurrence of the ONE entity.

Upon initial entry the form will retrieve an occurrence of the ONE entity using the primary key passed down by the parent form, then retrieve all associated occurrences of the MANY entity.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 4 - Maintain MANY in a ONE-to-MANY-to-ONE relationship

Description

This type of form is used to maintain the details of what is sometimes referred to as a MANY-to-MANY relationship. This can only be supported with the introduction of linking (cross-reference) entity which then produces a pair of ONE-to-MANY relationships, as shown in Figure 1.

Figure 1 - A typical ONE-to-MANY-to-ONE relationship

The primary key of the MANY entity is actually a combination of the primary keys from ONE A and ONE B. This means that only one occurrence of XREF can exist for a combination of primary key A and primary key B.

In this type of form the structure of the entities is as shown in Figure 2.

Figure 2 - Structure of the Multi 4 template

Only occurrences of MANY can be modified - both OUTER and INNER are read-only.

Note that no fields from entity MANY are displayed as it contains nothing but foreign key fields whose values are obtained from the two related entities.

This function will probably need two versions:-

• One where ONE A is used as OUTER and ONE B is used as INNER.
• One where ONE B is used as OUTER and ONE A is used as INNER.

Upon initial entry this function will perform an automatic retrieve of entity OUTER using the primary key passed down from the parent form. It will then retrieve all associated occurrences of MANY followed by an occurrence of INNER using the foreign key on MANY.

Buttons

OK	Will commit all updates to the database and return to the parent form.
CANCEL	Will abandon all outstanding updates and return to the parent form.
ADD	Will create a new occurrence of the MANY entity, with an empty INNER entity, and do one of the following, depending on the setting in local constant <AUTO_POPUP>:- <popup_id> Automatically call the named popup form without allowing a profile to be entered so that the user may choose an occurrence of the INNER entity. If no entry is selected the empty occurrence will be deleted. blank Wait for the user to press the button (or activate the <detail> trigger), which allows a profile to be entered beforehand. If no entry is selected the occurrence will remain empty. If an occurrence of INNER is selected which already has a link on MANY with the current OUTER it will be discarded with a DUPLICATE PRIMARY KEY message. The database will not be updated until the OK button is pressed.
DELETE	Will delete the current (highlighted) occurrence of the MANY entity from the screen. The database will not be updated until the OK button is pressed.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 4a - Maintain MANY in a ONE-to-MANY-to-ONE, with checkbox

Description

This type of form is similar to MULTI 4, but retrieves occurrences of entity INNER before those of entity MANY. The component structure is shown in Figure 3.

Figure 3 - Structure of the Multi 4a template

Upon initial entry this function will perform an automatic retrieve of entity OUTER using the primary key passed down from the parent form. It will then retrieve all available occurrences of INNER, then perform a lookup on MANY in determine the starting value of the SWITCH checkbox:-

• SWITCH will be ON (ticked) if an occurrence of MANY exists.
• SWITCH will be OFF (blank) if an occurrence of MANY does not exist.

Entries on entity MANY can be deleted by turning SWITCH from ON to OFF, or created by turning SWITCH from OFF to ON. This can be done either by clicking on the SWITCH checkbox or by double clicking on any other field within the line. This provides a very fast method of creating or deleting the link between ONE A and ONE B.

As this type of component retrieves all available occurrences of the INNER entity it may not be wise to use it if this table contains a large volume of occurrences. Consider using template MULTI 4b instead.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 4b - Maintain MANY in a ONE-to-MANY-to-ONE, with checkbox, with profile area

Description

This type of function is similar to MULTI 4a, but in cases where there can potentially be a large number of occurrences of entity INNER it may be useful to offer the facility of processing the data in subsets by using the profile area.

Upon initial entry this form will perform an automatic retrieve using a profile with ACCESS SWITCH set to ON so that only those occurrences of INNER where there is a linking entry on MANY will be displayed.

The ACCESS switch in the profile area is a tri-state checkbox:- ticked Will only show occurrences of INNER where an occurrence of MANY exists. blank Will only show occurrences of INNER where an occurrence of MANY does not exist. grey Will show occurrences of INNER whether an occurrence of MANY exists or not.

Entries on entity MANY can be deleted by turning ACCESS from ON to OFF, or created by turning ACCESS from OFF to ON. This can be done either by clicking on the ACCESS checkbox or by double clicking on any other field within the line.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 4c - Maintain MANY in a ONE-to-MANY-to-ONE, with navigation bar

Description

This is the same as MULTI 4, but with the addition of a navigation bar.

Upon initial entry this function will perform an automatic retrieve of entity OUTER using the primary key passed down from the parent form. It will then retrieve all associated occurrences of MANY followed by an occurrence of INNER using the foreign key on MANY.

Buttons

OK	Will commit all updates to the database and return to the parent form.
CANCEL	Will abandon all outstanding updates and return to the parent form.
ADD	Will create a new occurrence of the MANY entity, with an empty INNER entity, and do one of the following, depending on the setting in local constant <AUTO_POPUP>:- <popup_id> Automatically call the named popup form without allowing a profile to be entered so that the user may choose an occurrence of the INNER entity. If no entry is selected the empty occurrence will be deleted. blank Wait for the user to press the button (or activate the <detail> trigger), which allows a profile to be entered beforehand. If no entry is selected the occurrence will remain empty. If an occurrence of INNER is selected which already has a link on MANY with the current OUTER it will be discarded with a DUPLICATE PRIMARY KEY message. The database will not be updated until the OK button is pressed.
DELETE	Will delete the current (highlighted) occurrence of the MANY entity from the screen. The database will not be updated until the OK button is pressed.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 5 - Maintain MANY in a ONE(a)-to-MANY-to-ONE(b), with dynamic list for ONE(b)

Description

This type of function is similar to MULTI 4, but caters for a more complex form of linking (XREF) entity, as shown in Figure 4.

Figure 4 - ONE(a)-to-MANY-to-ONE(b), with dynamic list for ONE(b)

In this structure each occurrence of ONE B has its own set of occurrences on LIST B which identify those items where access can be switched ON or OFF (allowed or disallowed). Each occurrence of MANY (XREF) contains an indexed list of those items where the ACCESS ALLOWED switch has be changed from its initial setting.

The structure of this type of component is shown in Figure 5.

Figure 5 - Structure of the Multi 5 template

When the database is updated the indexed list on each occurrence of MANY is rebuilt to contain only those items from LIST (B) where the ACCESS ALLOWED switch has be changed from local constant <INITIAL_SETTING>. If the list is empty then the occurrence of MANY is deleted.

Local constant <INITIAL_SETTING> can be set at compile time to one of the following values:-

• 0 (OFF) - Access is OFF by default until it is turned ON.
• 1 (ON)  - Access is ON by default until it is turned OFF.

Buttons

OK	Will commit all updates to the database and return to the parent form.
CANCEL	Will abandon all outstanding updates and return to the parent form.
ADD	Will create a new occurrence of the MANY entity, with an empty INNER entity, and do one of the following, depending on the setting in local constant <AUTO_POPUP>:- <popup_id> Automatically call the named popup form without allowing a profile to be entered so that the user may choose an occurrence of the INNER entity. If no entry is selected the empty occurrence will be deleted. blank Wait for the user to press the button (or activate the <detail> trigger), which allows a profile to be entered beforehand. If no entry is selected the occurrence will remain empty. If an occurrence of INNER is selected which already has a link on MANY with the current OUTER it will be discarded with a DUPLICATE PRIMARY KEY message. All data from LIST will be shown with each ALLOWED switch set to the value of local constant <INITIAL_SETTING>. The database will not be updated until the OK button is pressed.
DELETE	Will remove the current occurrence of MANY and its associated INNER from the screen. The database will not be updated until the OK button is pressed.
STORE	Will commit all updates to the database but remain in the form.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Multi 5a - Maintain MANY in a ONE(a)-to-MANY-to-ONE(b), with dynamic list for ONE(a)

Description

This type of form is similar to MULTI 5, but caters for the situation where ONE B has to be the outer entity instead of ONE A.

The structure of this type of component is shown in Figure 6. You will notice that entity LIST is now inside entity OUTER instead of entity INNER. A dummy entity is placed inside INNER to hold the ACCESS ALLOWED switch and the LIST ITEM field.

Figure 6 - Structure of the Multi 5a template

Buttons

OK	Will commit all updates to the database and return to the parent form.
CANCEL	Will abandon all outstanding updates and return to the parent form.
ADD	Will create a new occurrence of the MANY entity, with an empty INNER entity, and do one of the following, depending on the setting in local constant <AUTO_POPUP>:- <popup_id> Automatically call the named popup form without allowing a profile to be entered so that the user may choose an occurrence of the INNER entity. If no entry is selected the empty occurrence will be deleted. blank Wait for the user to press the button (or activate the <detail> trigger), which allows a profile to be entered beforehand. If no entry is selected the occurrence will remain empty. If an occurrence of INNER is selected which already has a link on MANY with the current OUTER it will be discarded with a DUPLICATE PRIMARY KEY message. All data from LIST will be shown with each ALLOWED switch set to the value of local constant <INITIAL_SETTING>. The database will not be updated until the OK button is pressed.
DELETE	Will remove the current occurrence of MANY and its associated INNER from the screen. The database will not be updated until the OK button is pressed.
STORE	Will commit all updates to the database but remain in the form.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

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