19-04-2013, 03:18 PM
MS-ACCESS
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INTRODUCTION
Ms-access is a RDBMS developed by Microsoft Corp. MS Access DBs are preserved in the form of physical files with an extension .mdb (03) , .accdb (07 and 10).
Ms Access DBs are based on DB Objects like tables, queries, forms and reports.
MS Access allows to create Dbs in 3 ways
Table Property Sheet:
A property sheet consists of the characteristics of a particular selected field. Ms Access displays the PS of a field in the design view only. Some properties are validation text, validation rule, default value, required etc.
E.g. In validation, use <= or >= to set a range
Validation rule
A validation rule allows to restrict a range of values in the specified column. If the validation rule is violated then system defined error message will be displayed. This message can be customized through validation text property.
Primary Key
A primary key is a combination of not null and no duplicates feature . A table can have only one primary key for a field. If more than one field requires primary key feature, such can be treated as composite key.
Composite Key
A composite Primary Key allows to represent the primary key feature based on the specified fields data combined
Relationship in Ms-Access
A relationship specifies a data association in b/w multiple columns in same table or different tables. A relationship allows to control the data in a field based on the data of other fields. When multiple tables are related with each other, such tables are treated as parent and child tables.
A parent table consists of uniquely identified rows or records. A child table consists referenced data. A relationship requires a common field among the tables.
Types of Queries :
1. Simple (or) Select query : Used to retrieve the specific data from the specified tables
2. Updatable query: Used to update a specific field in the table with or without condition
3. Delete query: Used to remove the records from the table based on a specific condition.
4. Make table query : This allows to create a new table by executing the query.
5. Append query: Used to add new records to an existing table.
6. Cross Tab Query: Used to generate a pivot format data representation.