| Introduction to SQL |
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| What is Database? |
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| A database is an organized collection of data that
is useful to us. The data inside in a database can be modified, deleted
or new data can be added. They are stored in the form of
records as shown in the table below: |
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| The above table shows a single record. The columns-Associate_TID,
Associate_name, Age ,Commission are the fields or attributes, while
the row containing the corresponding the values-900678432, Smith,
28, 25000 is a single record. |
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| There can be a number of records in a table and
number of tables in a database. The tables in a database
are related to each other through one/more attributes/fields. |
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| A Database is diagrammatically shown below. It consists
of two tables-Associate and Asso_INFO. While Associate stores
information regarding an Associate TID, dept and salary, the
table Associate_INFO stores TID, name and date of join of the
Associate. The common link between the tables is established
by the field Asociate-TID. |
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| SQL Database Tables |
| As explained above, database is nothing but a collection of
inter-related tables. A table consists of rows and columns.
Rows are the records stored whereas columns are attributes or fields.
Each table is identified with a name e.g, Associate (Associate_Tid,
Associate_name, Age, Commission), suggesting Table named
Associate has four fields. |
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