What is validation rule in access

Within the Expression Element, Values, and Categories, there are several expressions present that you can easily apply over the selected field. Tap to the OK option, for applying it successfully. Now we will write a message which will pop-up to clarify the condition that applied above. For this, you just need to go to the fields tab and from the validation option tap to the Field Validation Message option.

Now type a message which you want to display when anyone enters any invalid data. Tap to the OK option to continue. Your entered validation message will pop-up when any invalid data is entered in the table. Thus, this will prevent you from making any data entry errors. Well, you can make use of Validation Text property and Validation Rule property of the form control for adding validation rule to any form or control.

This will ultimately help you to validate input data to that specific control and also restricts the user to insert invalid data. Note: creating a form automatically through the table by using the Form commands present on the menu bar ribbon will set the validation rule for the fields present in that particular table.

Well, a control may have several validation rules for the table fields and for the control that is bound. It is very helpful if anyone wants to set more restrictive rules as compared to the table. Firstly, you need to apply the form rule and after then table rule is to be set.

If the access table is much restrictive compared to form then rules which are defined for the table field will get the precedence. Eg: suppose you are applying following rule into the date field of the table:. But after then you apply the same rule on form control which is bounded to date field:.

Now the date field needs values before the year but here your form control needs dates that have a year or after the year Validation rules are a quiet useful feature of Access as it restricts the entrances of invalid data in your tables. Make use of this catchy MS Access feature to add validation rule in your Access database and prevent yourself from data entry error. Why is this important? Computers aren't as smart as humans about certain things.

While you might recognize that two and 2 or NC and North Carolina are the same thing, Access will not and therefore won't group these things together. Making sure to enter your data in a standard format will help you better organize, count, and understand it. Rules can also determine which options you have for working with your data.

For example, you can only do math with data entered in number or currency fields, and you can only format text entered into text fields. There are three main types of rules you can set for a field: data type , character limit , and validation rules. You shouldn't change field data type unless you are certain your field data is in the correct format for the new data type.

Changing a field containing only text to the Number type, for instance, will delete all of your field data. This process is often irreversible.

Setting the character limit for a field sets a rule about how many characters—letters, numbers, punctuation, and even spaces—can be entered into that field. This can help to keep the data in your records concise and even force users to enter data a certain way. In the example below, a user is entering records that include addresses.

If you set the character limit in the State field to 2 , users can only enter two characters of information. This means they must enter postal abbreviations for the states instead of the full name—here, NC instead of North Carolina. You might see a variety of other alert messages as you proceed. Read the instructions in each message, and then click Yes or No , as appropriate, to complete or stop the testing. You can use the Validation Rule property and the Validation Text property of a form control to validate data that is input to that control and to help users who input data that is not valid.

Tip: If you create a form automatically from a table by using one of the Form commands on the ribbon, any validation for fields in the underlying table are inherited by the corresponding controls on the form. A control can have a different validation rule from the table field to which the control is bound. This is useful if you want the form to be more restrictive than the table.

The form rule is applied, and then the table rule is applied. If the table is more restrictive than the form, the rule defined for the table field takes precedence. If the rules are mutually exclusive, they prevent you from entering any data at all. The date field now requires values earlier than the year , but the form control requires dates have that year or later, thus preventing you from entering any data at all.

Right-click the control that you want to change, and then click Properties to open the property sheet for the control. Click the All tab, and then enter your validation rule in the Validation Rule property box. Tip: Click the Build button to start the Expression Builder. Validation rules use Access expression syntax. For more information about expressions, see the article Introduction to expressions. Enter a value with a percent sign. For use with a field that stores number values as percentages.

Tests for values equal to existing members in a list. Comparison value must be a comma-separated list enclosed in parentheses. Tests for a range of values. You must use two comparison values — low and high — and you must separate those values with the AND separator. Forces users to enter values in the field. This is the same as setting the Required field property to Yes. However, when you enable the Required property and a user fails to enter a value, Access displays a somewhat unfriendly error message.

Note: You can also use AND to combine validation rules. You can use wildcard characters in your validation rules. Each of those standards uses a different set of wildcard characters. In the Access Options dialog box, click Object Designers.

Creating tables. Restrict data input by using validation rules. Need more help? Use the table's rule to compare fields. There is one trap to avoid. In some versions of Access, you will not be able to leave the field blank once you add the validation rule, i. If you need to be able to leave the field blank, add OR Is Null to your rule. Some versions accept Nulls anyway, but we recommend you make it explicit for clarity and consistency. This article explains how to use validation rules, and concludes with some thought provoking on when to use them.

When you select a field in table design, you see its Validation Rule property in the lower pane. This rule is applied when you enter data into the field. You cannot tab to the next field until you enter something that satisfies the rule, or undo your entry. In table design, open the Properties box and you see another Validation Rule.

This is the rule for the table.