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CLOSING LIBREOFFICE BASE
To close the application window of LibreOffice Base, click on the File Close or click on the Close (x) button of the
LibreOffice Base window.
WHAT ARE RELATIONSHIPS?
As we know, a database contains different related tables. Sometimes, we need data from different tables at the same
time. In such cases, these tables need to be linked based on a common field.
Relationships help you join two or more tables using a common field so that common data can be retrieved from
multiple tables at the same time.
The most important prerequisite for setting a relationship is that there must be a common field(s) between the two
tables to create a relationship. Also ensure that the data types of the common field in both the tables must be same.
If they are not same then LibreOffice Base will display an error message and will not allow to set the relationship
between the two tables.
Let us consider an example of a database containing following two tables—STUDENT and MARKS.
In STUDENT table - AdmNo is the primary key. In MARKS table - RollNo is the primary key and AdmNo is the foreign
key. So, each record in STUDENT table has a value of AdmNo that corresponds to a record in MARKS table with same
value of AdmNo.
Student Table
AdmNo Name Class Address Marks Table
1011 Arshia 12 RK Puram RollNo Admno UT Term 1 Term 2
1231 Advika 12 Defence Colony Marks Marks Marks
1411 Aekagra 10 Safdarjung 1 1231 89 81 91
1422 Divit 9 Preet Vihar 2 1411 80 85 92
1324 Akshaj 11 Jasola 3 1324 78 87 91
Once the relationship between the two tables has been set, the integrity of data will be managed by the DBMS. That
means once a student’s record has been entered in the STUDENT table, only then that Admission number can be
entered in the MARKS table. Thus, STUDENT table is called MASTER TABLE with master record while the MARKS table
is called the TRANSACTION TABLE with the corresponding record matching with master record is called as transaction
record.
The main advantages of Relating Tables in a Database are:
• A relationship can help prevent data redundancy and it saves time as the common data need not to be repeated in
different tables.
• It helps prevent missing data by keeping deleted data from getting out of sync. This is called referential integrity.
• Creating relationships between tables restricts the user from entering invalid data in the referenced fields.
• Any update in the master table is automatically reflected in the transaction tables.
Types of Relationships
There are three important types of relationship that can be created in a database which are as follows:
• One-to-One: In this type “One record of Master table is related to only one record of Transaction Table”. It is
represented as a 1:1 relationship.
Database Management System using LibreOffice Base 321

