![]() ![]() When you add a field, the Indexed property is set to No, which means Access doesn’t create an index. So how do you apply an index to a field? The trick is the Indexed field property, which is available for every data type except Attachment and OLE Object. Tables aren’t stored in sorted order, so there’s no way Access can be sure a given SSN isn’t in there unless it checks every record. But there’s one key principle-without an index, Access would need to check the entire table. In practice, all databases use many more optimizations to make this process blazingly fast. Once it finds the next “larger” SSN (one that falls later in the sort, like 001-02-5010), it knows the remainder of the index doesn’t contain a duplicate. If you enter the number 001-02-4300, Access needs to read only the first part of the list. This sorting is important, because it lets Access quickly check for duplicates. Sorting means the number 001-01-3455 always occurs before 002-40-3200 in the index, regardless of where the record is physically stored in the database. It’s important that the list of SSNs is sorted. Just set Required to Yes to stop the blank values, and set Allow Zero Length to No to prevent empty text. The good news is that if you find this whole distinction confusing, then you can prevent both blank values and empty text. However, you don’t receive an error message because empty text isn’t the same as a blank value. ![]() Here’s the strange part: Access automatically trims out spaces, and by doing so, it converts your single space to empty text. ![]() (Access stops you cold.) Now, try adding a new record, but place a single space in the field. Try inserting a new record and leaving the record blank. To try this out in your datasheet, create a Short Text field that has Required set to Yes. On the other hand, empty text indicates a conscious decision to leave that information out. A blank value could indicate an oversight-someone may just have forgotten to enter the value. Confused yet? The distinction exists because databases like Access need to recognize when information is missing. Empty text indicates that a field value was supplied, but it just happens to be empty. However, Access makes a slightly bizarre distinction between blank values and something called empty text.Ī blank (null) value indicates that no information was supplied. That’s because the Required property prevents only blank fields-fields that don’t have any information in them at all. However, with some data types you may want to add extra checks. Even though you don’t have all the information about this customer, you still need to place that customer in the Customers table so that he or she can receive the monthly newsletter.Īs a general rule, make a field optional if the information for it isn’t necessary or may not be available at the time the record is entered.Īccess supports this Required property for every data type. A potential customer may phone and leave only a mailing address (with no billing address, phone number, email information, and so on). The sales staff needs the flexibility to add a new prospect with only partial information. On the other hand, the same strictness is out of place in the same company’s Customers table. The Required field property is a great help here, because it prevents half-baked products from showing up in the catalog. You can verify the validity of a VAT number issued by any Member State / Northern Ireland by selecting that Member State / Northern Ireland from the drop-down menu provided, and entering the number to be validated.You need to think very carefully about what comprises the set of values you need, at a minimum, to create a record.įor example, a company selling Elvis costumes might not want to accept a new outfit into their Products table unless they have every detail in place. Moreover, any quote of “Member State” is replaced by “Member State / Northern Ireland” and any quote of “MS” is replaced by “MS / XI”.Īll traders seeking to validate UK (GB) VAT numbers may address their request to the UK Tax Administration. These VAT numbers are starting with the “XI” prefix, which may be found in the “Member State / Northern Ireland” drop down under the new entry “XI-Northern Ireland”. Due to specific upgrade works executed, the VIES on the Web application may not be accessible at all times during the following timeslot 19:00 CET - 21:00 CET.įor additional Information please contact TAXUD-VIESWEB at: of, the VoW service to validate UK (GB) VAT numbers ceased to exist while a new service to validate VAT numbers of businesses operating under the Protocol on Ireland and Northern Ireland appeared. ![]()
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