SheerPower® 4GL
A Guide to the SheerPower Language
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DESCRIPTION:

The FIELD option allows for record retrieval using a key field in a structure. SETUP's "SHOW FIELDS" menu option (see Chapter 16, Database Setup) displays the field names. The FIELD option is currently used only with the KEY or PARTIAL KEY option. The KEY option specifies the key to look for. The key is contained in str_expr.

The above example shows how to look in the CLIENT structure for an ID.

_EXTRACTED contains the number of records extracted. If the operation fails, _EXTRACTED will be 0 and an error message will be displayed.

15.9.3 SET STRUCTURE, FIELD: PARTIAL KEY

FORMAT:


        SET STRUCTURE struc_name, FIELD field_expr: PARTIAL KEY str_expr

EXAMPLE:

Example 15-46 SET STRUCTURE, FIELD: PARTIAL KEY 

  open structure cl: name 'sheerpower:samples\client' 
  input 'Name': name$ 
  set structure cl, field last: partial key name$ 
  print cl(id); ' '; cl(last) 
  end
  
 
Name? D 
80561 Derringer

DESCRIPTION:

This statement retrieves the first record matching the partial key in str_expr.

15.9.4 SET STRUCTURE: ID

FORMAT:


        SET STRUCTURE struc_name: ID str_expr

EXAMPLE:

Example 15-47 SET STRUCTURE: ID 

  declare structure str 
  open structure cl: name 'sheerpower:samples\client' 
  ask structure cl: id cl_id$ 
  set structure str: id cl_id$ 
  extract structure str 
  end extract
  for each str 
    print str(#1); ' '; str(#2) 
  next str 
  end
 
 
20000 Smith 
20001 Jones 
20002 Kent 
23422 Johnson 
32001 Waters 
43223 Errant 
80542 Brock 
80543 Cass 
80544 Porter 
80561 Derringer 
80573 Farmer

DESCRIPTION:

SET STRUCTURE: ID sets a structure to a structure ID that has been stored previously into a string variable with the ASK STRUCTURE: ID statement. Once the SET STRUCTURE: ID statement has been used, the structure with the new structure name (STR in the example) can be accessed. By using these statements, generalized routines can be written when the structure that will be accessed until runtime is not known.

15.9.5 SET STRUCTURE: POINTER

FORMAT:


        SET STRUCTURE struc_name: POINTER num_expr

EXAMPLE:

Example 15-48 SET STRUCTURE: POINTER 

  open structure cl: name 'sheerpower:samples\client' 
  extract structure cl 
  end extract
  set structure cl: pointer 3 
  print cl(id); ' ' ; cl(last) 
  end
 
 
23422 Johnson

DESCRIPTION:

This statement sets the structure to the nth record extracted. The statement is useful after an extract has been done because it provides random access to any record extracted. There is no error message if there are no records extracted, or if the number given is out of range. If the number is valid, _EXTRACTED is set to 1; otherwise, it is set to 0.

15.9.6 SET STRUCTURE: EXTRACTED 0

FORMAT:


        SET STRUCTURE struc_name: EXTRACTED 0

EXAMPLE:

Example 15-49 SET STRUCTURE: EXTRACTED 0 

  open structure vend: name 'sheerpower:samples\vendor' 
  set structure vend: extracted 0
  end

DESCRIPTION:

Setting the number of records extracted to zero causes a new collection to be started. The SET STRUCTURE struc_name : EXTRACTED 0 statement is used in conjunction with the EXTRACT STRUCTURE struc_name: APPEND statement.

15.10 Updating a Structure

Below is an example of opening an existing structure, extracting a record from it and updating the information in the record.

Example 15-50 Updating a Structure 

// Simple customer query 
open structure cust: name 'sheerpower:\samples\customer', access outin
do
  line input 'Customer number', default '12513': cust$ 
  if _exit or _back or cust$ = '' then exit do // get out if nothing to do 
  set structure cust, field custnbr: key cust$  // do the search 
  if _extracted = 0 then
    message error: 'Cannot find '; cust$ 
    repeat do
  end if
  print cust(custnbr), cust(name) 
  line input 'New name', default cust(name): newname$ 
  if _exit or _back then repeat do
  if newname$ = cust(name) then repeat do // nothing to do 
  cust(name) = newname$  // update the name 
  print 'Name changed to: '; cust(name) 
loop
end

Chapter 16
Database Setup

16.1 SETUP--Overview

SheerPower works with data in any database engine. SETUP tells SheerPower where data files are located and what database engines are used. Structures and definitions are the description of the data layout and it’s characteristics. Once structures have been defined with SETUP, SheerPower's structure statements can be used to manipulate the data.

SETUP supports the following database engines:

ARS
ODBC
FASTFILE
See Chapter 17, SheerPower and ODBC for instruction on using ODBC with SheerPower.

16.1.1 Entering SETUP

SETUP is entered by selecting SheerPower on the toolbar, then selecting Setup Data Structures.

Example 16-1 Entering SETUP

The OPEN STRUCTURE dialog box will open. If this is an existing structure, select the folder where it is stored, then select the file name.

If you are creating a new structure, choose the folder where it is to be stored and type in the file name.

Click on [Open] to open the structure.

Example 16-2 Open Structure

Once the structure has been opened, the STRUCTURE DEFINITION window will be displayed.

Example 16-3 Structure Definition Window

16.2 SETUP Structure Definition

This section describes the SETUP structure definition fields and options for answering them. Data fields inside the structure can be defined or modified. Field definitions can also be displayed in multiple formats.

Default answers are provided for many of the structure definition fields. You may either accept the default answer, or type in different information.

16.2.1 Structure Name

The NAME of the structure will default to be the same name as the file that you opened or created. The default extension for the file is .STR. The structure file contains:

The structure name can be any Windows file specification.

Clicking on the [...]button to the left of the structure NAME field will reopen the Open Structure dialog box. This allows you to choose a different structure name.

16.2.2 Database Engine

Click on the down arrow beside the DATABASE field to select the DATABASE ENGINE used by this structure.

Example 16-4 Selecting Database Engine

If this is a new structure, the default database engine will be ARS.

When modifying an existing data structure, the default will be the database engine specified in the structure file when it was originally setup.

16.2.3 Data Set

Inside the DATA SET field, type in the name of the DATA SET that will be used with this structure. If this is a new structure, the default data set name will be the same as the structure name. The default extension is .ARS.

Example 16-5 Data Set

The same data set can be used for a number of structures. For instance, you might use the CUSTOMER data set for both a CUSTOMER and a SALES structure: 


          structure files      data set 
 
             CUSTOMER.STR         | 
                         \        | 
                          \       v 
                           \
                            CUSTOMER.ARS 
                           / 
                          / 
                         / 
                SALES.STR

This can be useful when there are multiple uses for a set of data, but the access and definitions required should be different for each structure.

The data set name can be any Windows file specification.

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