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Invoicing database design
I am designing a database that includes the simple (!) functionality
of producing invoices (not an accounting package). I understand the convention is to have a table for invoice headers and one for invoice transactions. My question is what are the advantages of this approach rather than just having one table for invoice transactions. The printed invoice (an Access report) can have the invoice headings (date, invoice no customer address etc) in the report header and the invoice transactions in the report detail. What would be wrong with that? Gordon |
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Invoicing database design
"What would be wrong with that?"
Almost everything. The common design of a header and transactions in separate but related tables is always the correct way to accomplish this. If you had one table to hold it all, how many individual transactions could such a table hold? Well, with a limit of 256 fields in a table, you will run out very quickly. And if you are saying to repeat the header info for each transaction, then you are breaking the redundant data rule. And in the report, where will the header info come from? Or maybe I am missing the point and this post is a joke. wrote in message ... I am designing a database that includes the simple (!) functionality of producing invoices (not an accounting package). I understand the convention is to have a table for invoice headers and one for invoice transactions. My question is what are the advantages of this approach rather than just having one table for invoice transactions. The printed invoice (an Access report) can have the invoice headings (date, invoice no customer address etc) in the report header and the invoice transactions in the report detail. What would be wrong with that? Gordon |
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Invoicing database design
On 4 Nov, 14:21, "Klatuu" wrote:
"What would be wrong with that?" Almost everything. The common design of a header and transactions in separate but related tables is always the correct way to accomplish this. If you had one table to hold it all, how many individual transactions could such a table hold? *Well, with a limit of 256 fields in a table, you will run out very quickly. *And if you are saying to repeat the header info for each transaction, then you are breaking the redundant data rule. And in the report, where will the header info come from? Or maybe I am missing the point and this post is a wrote in message ... I am designing a database that includes the simple (!) *functionality of *producing invoices (not an accounting package). *I understand the convention is to have a table for invoice headers and one for invoice transactions. *My question is what are the advantages of this approach rather than just having one table for invoice transactions. *The printed invoice (an Access report) can have the invoice headings (date, invoice no customer address etc) in the report header and the invoice transactions in the report detail. *What would be wrong with that? Gordon- Hide quoted text - - Show quoted text - Wow, I feel as though I have been flamed. This is no joke. It was only a question on which I wanted advice. I said the invoicing function was simple, not the database itself. Fields in the one table invoicing transactions I envisage would be: invoice date invoice no customerID transaction date transaction ref productID item description Quantity Unit price As I see it, only the first 3 would break the redundant data rule. The data for the invoice report (including the header) would be built on the fly (using VBA) at time of invoice creation, drawing data not just from the invoice transaction table but also the related tables on customers/products etc. But thanks for responding - at least you confirmed the only objection to a one table design for invoice transactions is the data redundancy rule which in this particular case is not a great overhead if it saves having to maintain and update 2 tables. |
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Invoicing database design
Had I been asked I would have recommended against adding the last sentence to
the previous posting, but the other points are valid. My understanding of your proposed structure is different from Klatuu's, but in either case there are literally no arguments in favor of your approach in a relational database. It would make sense only in a flat database such as Excel. When a flat database is called for Excel is generally the better tool for the job, but a flat databse is not called for here. Are you planning to copy the invoice number and other invoice header information to each invoice item record? If so, is the only reason that you believe it would be less overhead than maintaining two separate tables? There are any number of objections to such an approach, one of which is that overhead is likely to be greater, not less. You would not throw all of your paper files into a large crate in the belief that a single container is less overhead than a series of file drawers. The analogy is imprecise, but still relevant. Among the problems I see is that you do not have a ready way to view a single invoice's information. One way would be to scroll through all of the records until you notice the number you want, then take note of when the number changes as you continue to scroll through the records. Another way would be to filter the recordset (or load a selective recordset) to view a single invoice. With a filtered recordset you would need to run the filter again to view the next batch of records. With invoice header information in a single table you could simply navigate to the next invoice to see all of that invoice's associated line items. The flat file approach will inevitably lead to a more awkward user interface. Another objection would be the possibility of data entry errors. You could avoid that to some extent by using code to copy the record, but that involves overhead. Another is that you cannot enforce unique invoice numbers at the table level. You could use code to check whether an invoice number has been used for a different customer on a different date or something, but again that is a lot of overhead, and probably difficult to construct. "Only" three fields breaking the redundant data rule is three more than I would accept. There is sometimes room for debate about what constitutes redundant data, but not in this case. Adding a related table is easy, and does not involve "maintenance" after it is created. Coding for a flat structure is where the overhead really starts to add up. wrote: "What would be wrong with that?" Almost everything. [quoted text clipped - 25 lines] - Show quoted text - Wow, I feel as though I have been flamed. This is no joke. It was only a question on which I wanted advice. I said the invoicing function was simple, not the database itself. Fields in the one table invoicing transactions I envisage would be: invoice date invoice no customerID transaction date transaction ref productID item description Quantity Unit price As I see it, only the first 3 would break the redundant data rule. The data for the invoice report (including the header) would be built on the fly (using VBA) at time of invoice creation, drawing data not just from the invoice transaction table but also the related tables on customers/products etc. But thanks for responding - at least you confirmed the only objection to a one table design for invoice transactions is the data redundancy rule which in this particular case is not a great overhead if it saves having to maintain and update 2 tables. -- Message posted via http://www.accessmonster.com |
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Invoicing database design
On 4 Nov, 16:01, "BruceM via AccessMonster.com" u54429@uwe wrote:
Had I been asked I would have recommended against adding the last sentence to the previous posting, but the other points are valid. *My understanding of your proposed structure is different from Klatuu's, but in either case there are literally no arguments in favor of your approach in a relational database. It would make sense only in a flat database such as Excel. *When a flat database is called for Excel is generally the better tool for the job, but a flat databse is not called for here. Are you planning to copy the invoice number and other invoice header information to each invoice item record? *If so, is the only reason that you believe it would be less overhead than maintaining two separate tables? There are any number of objections to such an approach, one of which is that overhead is likely to be greater, not less. *You would not throw all of your paper files into a large crate in the belief that a single container is less overhead than a series of file drawers. *The analogy is imprecise, but still relevant. Among the problems I see is that you do not have a ready way to view a single invoice's information. *One way would be to scroll through all of the records until you notice the number you want, then take note of when the number changes as you continue to scroll through the records. *Another way would be to filter the recordset (or load a selective recordset) to view a single invoice. *With a filtered recordset you would need to run the filter again to view the next batch of records. With invoice header information in a single table you could simply navigate to the next invoice to see all of that invoice's associated line items. *The flat file approach will inevitably lead to a more awkward user interface. Another objection would be the possibility of data entry errors. *You could avoid that to some extent by using code to copy the record, but that involves overhead. *Another is that you cannot enforce unique invoice numbers at the table level. *You could use code to check whether an invoice number has been used for a different customer on a different date or something, but again that is a lot of overhead, and probably difficult to construct. "Only" three fields breaking the redundant data rule is three more than I would accept. *There is sometimes room for debate about what constitutes redundant data, but not in this case. *Adding a related table is easy, and does not involve "maintenance" after it is created. *Coding for a flat structure is where the overhead really starts to add up. wrote: "What would be wrong with that?" Almost everything. [quoted text clipped - 25 lines] - Show quoted text - Wow, I feel as though I have been flamed. *This is no joke. It was only a question on which I wanted advice. I said the invoicing function was simple, not the database itself. Fields in the one table invoicing transactions I envisage would be: invoice date invoice no customerID transaction date transaction ref productID item description Quantity Unit price As I see it, only the first 3 would break the redundant data rule. The data for the invoice report (including the header) would be built on the fly (using VBA) at time of invoice creation, drawing data not just from the invoice transaction table but also the related tables on customers/products etc. But thanks for responding - at least you confirmed the only objection to a one table design for invoice transactions is the data redundancy rule which in this particular case is not a great overhead if it saves having to maintain and update 2 tables. -- Message posted viahttp://www.accessmonster.com- Hide quoted text - - Show quoted text - Hi Bruce, Thanks for your detailed post. You make a much more convincing argument which has won me over. Part of my reticence to construct an invoice header table and a separate one for invoice item lines lay in my ignorance of the approach I should take. I did say I was not designing an accounting system here but just the ability to print invoices. Can you give me some advice? I understand what fields should be in the 2 tables but am unclear how to populate them. The nature of the business is a service based one - charges are made to a range of clients for each enquiry handled. These are captured through a basic data entry screen, allocated to a client and populate an enquiries transaction table. What is the best approach then to populate the invoice header and invoice lines tables? Gordon |
#6
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Invoicing database design
Generally you would have something like the following:
tblInvoice (Invoice header table) InvoiceID (primary key, or PK) CustomerID InvoiceDate InitiatedBy Other information specific to the invoice tblDetails (line items or details for the invoice) DetailID (PK) InvoiceID Item UnitPrice Quantity InvoiceID needs to be the same data type (Number, Text) in both tables. If InvoiceID is an autonumber in tblInvoice, it needs to be Number (Long Integer) in tblDetails. Note that Number can be of various types. Long Integer, Double, and Currency are the ones used most of the time. Go to View Relationships. Add both tables. Drag InvoiceID from one table to InvoiceID on the other. Click Enforce Referential Integrity when the dialog appears. Note that the fields do not need to be the same name, but it may be easier to keep track of that way. Create a main form based on tblInvoice. From the toolbox, add a subform/subreport control, just as you would add a text box, line, or anthing else. With the subform control selected, click View Properties. Set its Source Object to tblDetails, and its Link Child and Link Master fields to InvoiceID if it is not already done. Click the three dots next to either Link property, and it should take you through the rest of the process. Add an Invoice record on the main form. On the subform, add a few line items (details). Create another Invoice record (main form) with a few line items. Go back to the first record. The line items should still be there. Look at the tables. Each Detail record should have a value in InvoiceID corresponding to an InvoiceID value in tblInvoice. In many cases there is a listing of items that may be added to Details. If you were dealing in products it would be a Products table. In the case of services there may be a listing of services and prices. In this case you would have a Services table: tblService ServiceID (PK Description UnitPrice Quantity tblDetails would look like this: tblDetails (line items or details for the invoice) DetailID (PK) InvoiceID ServiceID UnitPrice Quantity Add tblService to the Relationship window, and create a relationship between the ServiceID fields. Base the subform on tblDetails as before. Rather than Item you will be linking to tblService. Make a combo box. Set its Row Source to a query based on tblService. The first column (hidden) in the combo box is ServiceID. The other column(s) are visible, allowing you to select the item by name rather than number. Set the combo box Control Source to ServiceID. This is just a sketch, but I will have to leave it at that for now. For more information about design and general database principles, this is a list John Vinson often provides: Jeff Conrad's resources page: http://www.accessmvp.com/JConrad/acc...resources.html The Access Web resources page: http://www.mvps.org/access/resources/index.html Roger Carlson's tutorials, samples and tips: http://www.rogersaccesslibrary.com/ A free tutorial written by Crystal: http://allenbrowne.com/casu-22.html A video how-to series by Crystal: http://www.YouTube.com/user/LearnAccessByCrystal MVP Allen Browne's tutorials: http://allenbrowne.com/links.html#Tutorials Crystal's tutorial is as good a place as any to start, IMHO. To set up an incrementing Invoice number, one technique may be found he http://www.rogersaccesslibrary.com/f...ts.asp?TID=395 wrote: Had I been asked I would have recommended against adding the last sentence to the previous posting, but the other points are valid. Â*My understanding of [quoted text clipped - 76 lines] - Show quoted text - Hi Bruce, Thanks for your detailed post. You make a much more convincing argument which has won me over. Part of my reticence to construct an invoice header table and a separate one for invoice item lines lay in my ignorance of the approach I should take. I did say I was not designing an accounting system here but just the ability to print invoices. Can you give me some advice? I understand what fields should be in the 2 tables but am unclear how to populate them. The nature of the business is a service based one - charges are made to a range of clients for each enquiry handled. These are captured through a basic data entry screen, allocated to a client and populate an enquiries transaction table. What is the best approach then to populate the invoice header and invoice lines tables? Gordon -- Message posted via AccessMonster.com http://www.accessmonster.com/Uwe/For...esign/200911/1 |
#7
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Invoicing database design
On Nov 5, 2:06*pm, "BruceM via AccessMonster.com" u54429@uwe wrote:
Generally you would have something like the following: tblInvoice (Invoice header table) * *InvoiceID (primary key, or PK) * *CustomerID * *InvoiceDate * *InitiatedBy * *Other information specific to the invoice tblDetails (line items or details for the invoice) * *DetailID (PK) * *InvoiceID * *Item * *UnitPrice * *Quantity InvoiceID needs to be the same data type (Number, Text) in both tables. *If InvoiceID is an autonumber in tblInvoice, it needs to be Number (Long Integer) in tblDetails. *Note that Number can be of various types. *Long Integer, Double, and Currency are the ones used most of the time. Go to View Relationships. *Add both tables. *Drag InvoiceID from one table to InvoiceID on the other. *Click Enforce Referential Integrity when the dialog appears. *Note that the fields do not need to be the same name, but it may be easier to keep track of that way. Create a main form based on tblInvoice. *From the toolbox, add a subform/subreport control, just as you would add a text box, line, or anthing else. *With the subform control selected, click View Properties. *Set its Source Object to tblDetails, and its Link Child and Link Master fields to InvoiceID if it is not already done. *Click the three dots next to either Link property, and it should take you through the rest of the process. Add an Invoice record on the main form. *On the subform, add a few line items (details). *Create another Invoice record (main form) with a few line items. Go back to the first record. *The line items should still be there. *Look at the tables. *Each Detail record should have a value in InvoiceID corresponding to an InvoiceID value in tblInvoice. In many cases there is a listing of items that may be added to Details. *If you were dealing in products it would be a Products table. *In the case of services there may be a listing of services and prices. *In this case you would have a Services table: tblService * *ServiceID (PK * *Description * *UnitPrice * *Quantity tblDetails would look like this: tblDetails (line items or details for the invoice) * *DetailID (PK) * *InvoiceID * *ServiceID * *UnitPrice * *Quantity Add tblService to the Relationship window, and create a relationship between the ServiceID fields. Base the subform on tblDetails as before. *Rather than Item you will be linking to tblService. *Make a combo box. *Set its Row Source to a query based on tblService. *The first column (hidden) in the combo box is ServiceID. The other column(s) are visible, allowing you to select the item by name rather than number. *Set the combo box Control Source to ServiceID. This is just a sketch, but I will have to leave it at that for now. *For more information about design and general database principles, this is a list John Vinson often provides: Jeff Conrad's resources page:http://www.accessmvp.com/JConrad/acc...resources.html The Access Web resources page:http://www.mvps.org/access/resources/index.html Roger Carlson's tutorials, samples and tips:http://www.rogersaccesslibrary.com/ A free tutorial written by Crystal:http://allenbrowne.com/casu-22.html A video how-to series by Crystal:http://www.YouTube.com/user/LearnAccessByCrystal MVP Allen Browne's tutorials:http://allenbrowne.com/links.html#Tutorials Crystal's tutorial is as good a place as any to start, IMHO. To set up an incrementing Invoice number, one technique may be found hehttp://www.rogersaccesslibrary.com/f...ts.asp?TID=395 wrote: Had I been asked I would have recommended against adding the last sentence to the previous posting, but the other points are valid. *My understanding of [quoted text clipped - 76 lines] - Show quoted text - Hi Bruce, *Thanks for your detailed post. *You make a much more convincing argument which has won me over. *Part of my reticence to construct an invoice header table and a separate one for invoice item lines lay in my ignorance of the approach I should take. *I did say I was not designing an accounting system here but just the ability to print invoices. Can you give me some advice? I understand what fields should be in the 2 tables but am unclear how to populate them. The nature of the business is *a service based one - charges are made to a range of clients for each enquiry handled. *These are captured through a basic data entry screen, allocated to a client and populate an enquiries transaction table. *What is the best approach then to populate the invoice header and invoice lines tables? Gordon -- Message posted via AccessMonster.comhttp://www.accessmonster.com/Uwe/Forums.aspx/access-tablesdbdesign/20...- Hide quoted text - - Show quoted text - Hey, thanks for taking the time to spell all that out for me. I really appreciate that. I think I was looking for a different solution, which reflected the work flow process. You see, all those enquiries I talked about are entered through the month, then at the end of the month I was looking to devise a routine that with the click of a button would print out for each client an invoice (Access report) listing the summary details of each charged for enquiry processed that month with a unit price etc and a total invoice charge. The enquiries table would then be updated with a flag (tick box) or the invoice no/ ID showing that the enquiry had been invoiced. Perhaps that solution is a bridge too far and I should concentrate on devising a main form/subform combination - combo box with clients in the main form, enquiries relative to that client in the subform, with a button to click to produce an individual invoice for that client for all outstanding (ie uninvoiced) enquiries. In doing that I could put some codein ther at the same time to write the relevant data to an invoice header file and an invoice transactions file. Does that seem feasible to you or can you think of a better approach? Gordon |
#9
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Invoicing database design
On 5 Nov, 20:34, "BruceM via AccessMonster.com" u54429@uwe wrote:
Are you saying there are invoices with several line items, and that there may be several such invoices per month for a client? *If so, are you further saying that if there are three invoices per month for a customer, each invoice with three line items, that you want the summary report to show all nine line items, or that you want it to show three lines: *the summaries of the individual invoices? Either may be done, but if you are summarizing an invoice into a single line what detail information can you show other than grand total? *You could add up the total quantity, but that may not make sense if the three line items are for different things. It could be that the report's Sorting and Grouping capabilities could give you what you need. *However, I need to stress that if you have a conventional invoice system with several line items grouped under a single invoice number, you should proceed with related tables. *If you are set up properly on that first level any big picture data can be produced. *This is true on every level. *If your design is properly normalized you can do almost anything with the data. I am struggling to convert a project from my earlier Access days that is not properly normalized. *On some things I knew better but decided it was too much bother. *On others I just didn't know better. *Both are proving equally vexing now. wrote: Generally you would have something like the following: [quoted text clipped - 112 lines] - Show quoted text - Hey, thanks for taking the time to spell all that out for me. *I really appreciate that. *I think I was looking for a different solution, which reflected the work flow process. *You see, all those enquiries I talked about are entered through the month, then at the end of the month I was looking to devise a routine that with the click of a button would print out for each client an invoice (Access report) listing the summary details of each charged for enquiry processed that month with a unit price etc and a total invoice charge. *The enquiries table would then be updated with a flag (tick box) or the invoice no/ ID showing that the enquiry had been invoiced. Perhaps that solution is a bridge too far and I should concentrate on devising a main form/subform combination - combo box with clients in the main form, enquiries relative to that client in the subform, with a button to click to produce an individual invoice for that client for all outstanding (ie uninvoiced) enquiries. *In doing that I could put some codein ther at the same time to write the relevant data to an invoice header file and an invoice transactions file. *Does that seem feasible to you or can you think of a better approach? Gordon -- Message posted via AccessMonster.comhttp://www.accessmonster.com/Uwe/Forums.aspx/access-tablesdbdesign/20...- Hide quoted text - - Show quoted text - Normally only 1 invoice per client per month - that invoice could have one or more item lines (each one representing a unique enquiry with its own characteristics). I have a table of those enquiries - what I am struggling with is how do I convert the enquiries into invoice item lines and invoice headers without going through each client and creating an invoice header and then selecting the item lines to add to that invoice or worse still re-keying the item lines (enquiries). Unless you can suddenly see what I am driving at (which cannot be easy I know), I will adopt the approach I outlined in my previous post above. Gordon |
#10
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Invoicing database design
It sounds as if your term for line items is enquiry. It would help to know a
little more about the structure, but I will use part of the field list you showed in an earlier post as a starting point. Work on a copy of the database, of course. invoice date invoice no customerID productID item description Quantity Unit price I will assume InvoiceDate, InvoiceNo, and CustomerID are header items, and the rest are line items, or enquiries. I will asume further that the InvoiceDate is the same for all records with a particular InvoiceNo. Same for CustomerID. You could make a SELECT DISTINCT query of InvoiceDate, InvoiceNo, and CustomerID, or a totals query in which you group on those three fields. In any case the query will include just the header fields, and will show only unique records. Use the query to make a table containing the same information. This could be a make-table query, or I think you can copy a query and paste it as a table. There are other adaptations you could use, but in the end there will be only one record per InvoiceNo. Now make a copy of the original table. Delete InvoiceDate and CustomerID fields. Create a one-to-many relationship between CustomerID in the Header table created from the query and CustomerID in this new Details table. Use the Header table as the basis for an Invoice form, and the Details table as the basis for a subform as described in the posting in which I sketched the table structure. This should leave you with Header (Invoice) information on the main form and related LineItem/Detail/Enquiry records on the subform. Whatever the details, the general idea is that repeated Header information will be consolidated into one table with no repetition, and Header fields deleted from a copy of the original table to leave you with the Detail information. As for printing a report, you could filter or group the records as needed, but I am not clear on how TransactionDate from your original posting of table structure fits into this. I assume it is part of a Detail record, but I don't know if the TransactionDate month will always be the same as the InvoiceDate month. You can make it do what you want either way, but it is a little more involved if the Header and Detail months are not the same in all cases. BTW, whenever I mention basing a form on a table you could (and probably should) use a query based on the table instead. This will allow you to sort by InvoiceNunber, among other things. wrote: Are you saying there are invoices with several line items, and that there may be several such invoices per month for a client? Â*If so, are you further [quoted text clipped - 54 lines] - Show quoted text - Normally only 1 invoice per client per month - that invoice could have one or more item lines (each one representing a unique enquiry with its own characteristics). I have a table of those enquiries - what I am struggling with is how do I convert the enquiries into invoice item lines and invoice headers without going through each client and creating an invoice header and then selecting the item lines to add to that invoice or worse still re-keying the item lines (enquiries). Unless you can suddenly see what I am driving at (which cannot be easy I know), I will adopt the approach I outlined in my previous post above. Gordon -- Message posted via http://www.accessmonster.com |
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