Access2007 Basic Tutorial: 5 Steps Design Method

Source: Internet
Author: User
Tags numeric table name valid

Don't waste the effect of data types

When you want to store digital data, you might want to specify a numeric data type. Before you do so, please consider the purpose of the data first. For example, you wouldn't use a block number or a zip code for a mathematical equation. In this case, save your data as text. You will save some memory, but more importantly, the data type is based on the data used. If you need to use a literal value as a true number, you can use the Val () function "=val" (this field stores numeric or literal values) in the field that represents the text field in the table.

Use the size of the most appropriate domain

Since today's systems are so powerful, it is no longer an urgent task to specify the size of the most appropriate domain. However, in order to better implement the work, developers will still be able to limit the size of the domain. The first step you need to take is to get the data into effect. For example, you store state names in a text field with a domain size of 2. If the user enters Ark instead of ak,access, the input will be rejected. Of course, the properties of the domain size will only reject entries that are too large to be able to detect input or other errors. This field will still accept other incorrect entries, such as "A" or "K6".

This can also be applied to a number field, but not to a well-defined range. For example, a byte field can accept values ranging from 0 to 255, while a long integer field can accept values ranging from 2,147,483,648 to 2,147,483,647.

Select the appropriate data type and domain size properties for each domain. Always select the smallest data type and the size of the field, it is possible to hold the largest value in this field.

Using Profiling Tools

Access has two tools to help you refine your design. The first is the Table Analyzer Wizard, which is able to examine a table and make it as appropriate for you to recommend a change. Second, the Performance Analyzer, which is able to check your entire database and make recommendations for improving the design. Usually, you will use the advice that the wizard puts forward.

No matter which wizard you want to run, you can select the appropriate item from the Analyzer in the Tools menu.

Don't forget the properties of the table

Like fields, tables have properties that can define their purpose. Most of them can resolve themselves, and the default properties are usually adequate. To access these properties, you only need to open the table in Design view, and then select Properties from the View menu. Here are some things you should know:

Sort by: Specify an arrangement order, and access can apply it when you open the table. Just type the name of the field according to the record you want sorted. If you do not use this setting, access sorts by the primary key. If you do not have a primary key, access is displayed in the order in which the data is entered. It doesn't have much to do with the surface because the user doesn't see the table. However, as with many domain properties, bundled objects inherit properties.

Subdatasheet Name: It determines whether the subdatasheet displays related records. Many people feel that a subdatasheet is annoying, and if you think so, you can set this property to [None] to disable it.

Pay attention to the limits of the range

Although you may never be exposed to the setting of a table boundary range, you must know that they exist:

A table name can contain up to 64 characters.

The number of domain names can contain 64 characters.

Each table can contain a maximum of 255 domains.

The table size is limited to 2GB minus the amount of space required by the system object.

The number of text fields can store 255 characters.

When you enter data through the user interface, the Memo field can store up to 65,535 characters. If you enter data from a program, it can accept up to 1GB of size.

OLE fields can support up to 1GB sizes.

Each table can have up to 32 indexes.

Each index can contain up to 10 domains.

A valid rule expression can store up to 2045 characters, and a valid text property can have more than 255 characters.

A Description property can store up to 255 characters.

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