After creating the table structure, you can enter records into the table. This is called populating the table. The records are entered into the table in similar way as data is entered into the spreadsheet. The database software also allows you to create a data ‘Form” through which you can enter or modify records very easily. Use of forms is very easy method to enter data into table.
You can also apply different validation rules on data fields. For example, you can apply a validation rule on a numeric field to accept the data between 0 to 100 values only. As you enter the data, the DBMS checks or validates the data and displays a message if data entry is invalid. The validation is very important feature because it helps to enter the correct data into the’ tables of database.
Displaying Records
Once records are entered into tables of a database, these can be displayed again on the screen for editing or printing on the printer. If you are displaying records on the screen then you can see the data of only those records that fit on the screen. The data of all records can be displayed by scrolling up, down, right, left through scroll bars.
You can also see or print the data of selective fields of each record. Similarly the selective records can be printed or displayed by filtering the records of database. In filtering process only those records are retrieved from. the database that satisfy the given criteria or condition. It is called filter because only those records are displayed that fulfill the given criteria and remaining records that do not fulfill the criteria are filtered out. For example, displaying those records from table of “student” database that have value greater than 750 in the “marks” field.
Deleting Records
You can also delete the records from the tables of the database. MS-Access displays a confirmation dialog box to confirm the deletion. The deleted records are permanently deleted from the tables of the database.
Sorting Records
Normally records are displayed or retrieved from the tables of database in the same order in which they are entered. DBMS has a very, powerful feature to sort the records of database table according to the contents of one or more fields. You can sort records into particular order such as alphabetical, numerical or by date etc. The records can be sorted into ascending or descending order. In ascending order, records are organized or arranged from “A” to “Z” and “a” to “z” alphabetically or from 0 to 9 numerically. In descending order, records are arranged in opposite order as compare to ascending order.
DBMS software also has important feature to import data from different files of different formats and store into the database tables as records. For example you can import data from a spreadsheet or text file into a database file.
Querying a Database
A query means “a request” or “a question”. You can also retrieve specific records from database by running a query. A query is a statement that specifies which data is to be retrieved from the database according to the given criteria. The specified data can be very easily retrieved from multiple tables of database by using the query. In other words a query is .a more powerful type of filter that is used to access data of relational database. Through query, you can also delete records, update records, sort records etc.
A query is like an English statement that contains the name of table, names of fields of the table, criteria and other options. Suppose you have a database “student” having two tables. One named as “Address” containing records of students with complete addresses. The other table “Marks” containing records of marks of students. Suppose you want to access the recor.ds of students that belong to Lahore and got marks greater than 700. You also want to get the data of two fields “Name” and “Father-name” from “Address” table and. data of three fields “Math”“Computer” and “Total” from “Marks” table. You can setup a query or statement by specifying the table names, field names and criteria. Some database software provides special windows for creating queries.
