Wizard of substitutions, Properties of zeros - Informatics for economists

Wildcard Wizard

In addition to the nine data types listed above, Access provides the Wildcard Wizard , which in particular helps fill foreign key fields without violating data integrity. In addition, the wizard helps you set the substitution properties for the code field of the main table in such a way that instead of the codes, more informative values ​​from the lookup table will be visible.

In the first window of the wizard, you need to choose from where the column of substitutions gets the values: from a fixed set (and then this column you will have to enter in the next Wizard window) or from another table or query.

In the next window, select the table that contains the substitution values. Next, select the fields of the table that you want to include in the substitution list (include the key field and one or more descriptive fields that will help you distinguish the elements of the substitution column).

Properties of zeros

For each field of the table, you can set property values ​​(Table 10.2), the list of which depends on the selected data type. Some property values ​​are set by default.

Comment on some properties.

For character data, the text data type is usually chosen. The Field Size property specifies the amount of memory required to store data (the default is 255 characters -

Table 10.2

Field Properties

Property

Assignment

Field Size

Specifies the maximum number of characters to enter in this field

New Values ​​

Specifies how to generate new values ​​for the counter field

Field format

Specifies the output format for this field

The number of decimals

Specifies the number of decimal places to use when displaying numbers

Input mask

Specifies an input mask that facilitates entering data in the field

Signature

Defines a more meaningful field name, which is output as a field signature

The default value

Lets you specify a value that is automatically entered in the field when creating a new record

Condition on value

Defines the requirements for data entered in the field

Error message

Lets you specify the text of the message that appears on the screen if the entered data violates the condition specified in the Condition on value property

Required

field

Specifies whether the required field requires a value

Blank lines

Determines whether blank lines are allowed in this field ( )

Indexed field

Defines an index created by a single field

oxen). By specifying the maximum length of the text field in the Field Size property, you can save the memory needed to store the data. For example, it's obvious that for Company name in the example above, it's enough to set the size of the field to 20 characters.

The Signature property. Despite the fact that MS Access allows to use spaces in any names, it is more reasonable to dispense with field names without spaces. Then you can use the Signature property to specify a more meaningful name for the spaces with the field that MS Access will display in the form controls and in the report headers.

The Condition on value property property. The specified condition will always be checked when you enter or change the field value in the table. MS Access will not allow you to enter data that does not satisfy this condition.

The condition on the value is given by an expression that consists of comparison operators and operands.

Comparison operators: & lt ;, & lt; =, & gt ;, & gt; =, =, & lt; & gt; IN (checked for equality to any value from the list), BETWEEN (it is checked that the field value is within the specified range; the upper and lower boundaries are separated by the AND operator); LIKE (check the correspondence of the text field to the specified character pattern).

If the expression does not contain an operator, Access uses the = operator. You can use several comparisons associated with logical operators OR, AND.

Text values ​​must always be enclosed in quotation marks. For example, to limit the entry in the Company name field by the two Sitilink and Lizarin firms, you can use the following expressions as the condition for the value for this zero: Sitilink OR Lizarin or IN ( Sitilink & quot ;, Lizarin ). If the date is used as the operand, it must be enclosed in the symbols #, for example BETWEEN # 01/01/2010 # AND # 31/12/2010 #. Then MS Access will allow to enter in this field only the data for 2010.

The LIKE statement checks the text field for a given character pattern. The following wildcards are used to specify the pattern:

•? - one arbitrary character;

• * - any (including zero) number of arbitrary characters; is used to replace a sequence of characters;

• # - one arbitrary number;

• [] - allow you to define a condition so that a specific position of the text field contains only the characters indicated in square brackets; [A-Z] is any letter; [0-9] is any digit;

•! - allows you to define a condition to indicate that a particular position can contain any ns in the symbol: LIKE condition [! 0-9AB] checks a string starting with any character except the number and letters A and B.

Indexed field. The index is an MS Access tool that accelerates searching and sorting in a table. The table's key field is automatically indexed. It is not allowed to create indexes for MEMO type fields and hyperlink or OLE object fields.

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