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Why can a validation rule not stop incorrect information from being entered into the database?
Wiki User
∙ 9y ago
A validation rule must allow all possible valid answers. For example, a person's age must be, say, between 0 and 130 years. An age less than zero, or more than 130, would be rejected. However, there is no way to automatically verify that the age is correct. For example, if my age is 48 years, and somebody types 58, or 38, instead, the only way to verify that this is correct is to go back to the source (for example, asking the person, or checking documents).
Wiki User
∙ 9y ago
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What is a therom?
Techniques used for validation and verification Data entered into a database or spreadsheet is usually checked using processes called validation and verification. Validation is an automatic computer check to ensure that the data entered is sensible, reasonable, complete and within acceptable boundaries. It does not check the accuracy of data. The checking of the data entered is done by software that can either be part of the input system or a separate program that checks the data. Types of validation There are a number of validation types that can be used to check the data that is being entered. · Range check: checks that a value falls within the specified range, it will reject any data items outside an expected range. For example, number of hours worked must be less than 50 and more than 0. · Presence check: checks that data has been entered into a field, it will reject the data where the required fields have been left blank. For example, in most databases a key field cannot be left blank. · Length check: ensures that the data entered is of reasonable length. For example, a password which needs to be six letters long. · Type check: ensures data is of a particular data type. For example, a number of items in stock will be entered as an integer (whole number). · Format check: ensures a data item matches a pre-determined pattern of letters and/or numbers. For example, a National Insurance number is in the form LL 99 99 99 L where L is any letter and 9 is any number · Lookup checks: ensures that data matches one of a limited number of valid entries. For example subjects studied in a school should be selected from a list of Mathematics, English etc. Verification is a process used to check that the data has been entered accurately, is consistent and has not been corrupted. Verification confirms the integrity of data as it is copied between different parts of a computer system. Copying should not change the data. Differences detected would mean an error in the transfer. Types of verification The verification checks may include:- · Double entry verification: to ensure data typed into a computer system is entered accurately. The data is entered twice, by different operators, and compared by the system. Any differences can be identified and manually corrected. · Visual verification: data is entered and the original data is compared to the data entered into the system; for example by comparing the data on the data on the data capture form with a printout of the database, or with the entered data on the screen.
How do related tables improve the accuracy of a data in a database?
In short, they do not. Relating tables in a database defines the relationships between the data sets in the different tables and allows the data to be accessed more efficiently, but it does not affect the accuracy of the data entered.
How do you read a barcode without a barcode scanner?
BArcodes have an ISBN attached . This is the number seen beneath the barcode. Its the unique product identifier and can also be used to recognise the product once entered in the recognition database
Do Primary keys have to be numbers that are entered by the user?
Primary keys have to be numbers that are entered by the user.
Two principal integrity rules for the relational model?
Integrity Rules Although integrity rules are not part of normal forms, they are definitely part of the database design process. Integrity rules are broken into two categories. They include overall integrity rules and database-specific integrity rules. == The two types of overall integrity rules are referential integrity rules and entity integrity rules. Referential integrity rules dictate that a database does not contain orphan foreign key values. This means thatEntity integrity dictates that the primary key value cannot be Null. This rule applies not only to single-column primary keys, but also to multi-column primary keys. In fact, in a multi-column primary key, no field in the primary key can be Null. This makes sense because, if any part of the primary key can be Null, the primary key can no longer act as a unique identifier for the row. Fortunately, the Access Database Engine (Access 2007's new version of the JET database engine, available with the new ACCDB file format) does not allow a field in a primary key to be Null.Database-Specific Rules The other set of rules applied to a database are not applicable to all databases but are, instead, dictated by business rules that apply to a specific application. Database-specific rules are as important as overall integrity rules. They ensure that only valid data is entered into a database. An example of a database-specific integrity rule is that the delivery date for an order must fall after the order date.
Explain why validation cannot stop incorrect information from being entered into a database?
Because it just checks if the wrong data has been entered in the wrong field.
Why do you used validation?
A validation rule is simply to make sure that the data is entered correctly into the database (go onto bitesize-ICT-validation and verification for more info)
Why do you use validation rules?
A validation rule is simply to make sure that the data is entered correctly into the database (go onto bitesize-ICT-validation and verification for more info)
How can you restrict the values of data entered into a database?
By creating Data validation rules you should be able to restrict the values of data entered
What is field validation?
Field validation ensures that a program or form is using clean incorrect data. A set of validation rules are used to check data that is entered into a system before it is processed.
What data validation rule is cautionary?
Data validation is all about what can be entered into a spreadsheet cell or database cell, you can choose an error message aswell as restricting what values can be entered, reducing human error and improving accuracy.
Data validation best refers to?
Data Validation is a process that ensures that data entered into the database form, a web form, or a computer program conforms to the correct data type.
What is the difference between field level and record level validation rule?
The information entered and how the information is entered is a very dominate role in field/record level validation. However they share the same goal to enforce rules consistently, to write less code.
What are the advantages and disadvantages of validation?
The advantages are: It stops the user from entering data that may be incorrect. It also reduces the chance of wrong data being entered by mistake. The disadvantage is: It will take longer for the programmer to script the validation code.
Why are the validation error messages important on Microsoft Excel?
They tell the user that they have entered incorrect data and should tell them what they have done wrong and what is acceptable. Without the messages, the user will not know what the problem is.
Which features restrict the entry of excel cell?
Validation allows users to restrict what can be entered, by setting up validation rules, like specifying a minimum value that can be entered, or that a cell can only accept dates for example. There are a lot of other ways validation can be used.
Enter on the database or in the database?
We would use in rather than on. Data is stored in a database, not on a database. Data is entered into a database not onto a database.
