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The Tables of a Database

 

Tables Fundamentals

 

Introduction

As we saw when studying data sets, a table is one or more lists of items. If the table is only one list of items, these items are identical in nature. Here is an example:

Judie
Ernest
Bill
David
Hermine

If the table is made of more than one list, each list is made in a distinguishable category. Here is an example:

Name Age Gender Relationship
Judie 18 Female Sister
Ernest 24 Male Cousin
Bill 52 Unknown Uncle
David 36 Male Brother
Hermine 12 Unknown Niece

Based on this, a list is simply an arrangement of information and this information, also called data, is stored in tables.

Practical LearningPractical Learning: Introducing Database Tables

  1. Start Microsoft Visual Basic
  2. If the Server Explorer is not visible, on the main menu, click View -> Server Explorer.
    In the Server Explorer, right-click Data Connections and click Create New SQL Server Database
  3. In the Server Name combo box, select the server or type (local)
  4. Accept or specify your authentication mode
  5. Set the name of the database to CPAR1 and click OK

Visual Creation of a Table

The information of a table is organized in categories called columns. To visually create a table in Microsoft SQL Server, first open the SQL Server Management Studio. In the Object Explorer, locate and expand the database for which you are creating the table. Then right-click the Tables node and click New Table. A window would come up and wait for you to proceed:

Table

To visually create a table in Microsoft Visual Studio, in the Server Explorer, expand the connection to the database that will own the table. Right-click the Tables node and click Add New Table:

Add New Table

After clicking Add New Table, a new empty table would come up and expect you to take charge:

New Table

Practical LearningPractical Learning: Starting a Table

  1. In the Server Explorer, expand server.CPARr1.dbo
  2. Under it, right-click Tables and click Add New Table

Tables Names

To complete the creation of a table, you must save it. If you are freshly creating a table and decide to save it, you would be prompted to name it. The name of a table:

  • Can be made of digits only. For example you can have a table named 148
  • Can start with a digit, a letter, or an underscore
  • Can be made of letters, digits, and spaces

Besides these rules, you can make up yours. To avoid confusion, here are the rules we will use to name our tables:

  • A name will start with a letter. Examples are act or Second
  • After the first character, the name will have combinations of underscores, letters, and digits. Examples are _n24, act_52_t
  • Unless stated otherwise, a name will not include special characters such as !, @, #, $, %, ^, &, or *
  • If the name is a combination of words, each word will start in uppercase. Examples are Staff Members or Video Titles

Creating a Table With SQL

 

Introduction

In SQL, to create a table, you start with the following statement:

CREATE TABLE TableName;

The CREATE TABLE expression is required. The TableName factor specifies the name of the new table. The TableName can use the rules and suggestions we reviewed for the tables.

Using Sample Code

To assist you with creating a table, Microsoft SQL Server can generate sample code for you. You can then simply modify or customize it. In Microsoft SQL Server Management Studio, first display or open an empty query window. To display the Templates Explorer, on the main menu, you can click View -> Templates Explorer. In the Templates Explorer, expand the Table node. Under table, drag Create Table and drop it in the query window. Sample code would be generated for you.

Tables Maintenance

 

Viewing the Properties of a Table

Table maintenance consists of reviewing or changing its aspects. This includes reviewing the list of tables of a database, renaming a table, or deleting it.

Like every other object of a database or of the computer, a table possesses some characteristics that are proper to it. To view these characteristics in Microsoft SQL Server Management Studio, in the Object Explorer, you can right-click the table and click Properties.

Opening a Table

Most operations require that you open a table before using it. There are various ways a table displays, depending on how you want to examine it:

  • In Microsoft SQL Server Management Studio:
    • To view the structure of a table, perhaps to change its columns, in the Object Explorer, expand your database and its Tables node. Right-click the table and click Modify. The table would open in design view, the same view you use to visually create a table.
    • If you want to view the SQL code of a table, in the Object Explorer, right-click the table, position the mouse on Script Table AS, CREATE To, and click New Query Editor Window
    • To open a table to view its data, perhaps to perform data entry, in the Object Explorer, right-click the table and click Open Table
  • In Microsoft Visual Studio, in the Server Explorer, expand the connection to the desired database and expand its Tables node:
    • To view the structure of a table, right-click the table and click Open Table Definition
    • To open a table to view its data, right-click the table and click Show Table Data

Tables Review

In Microsoft Visual Studio, to see the list of tables of a database, in the Server Explorer, expand the connection to the desired database and expand the Tables node. Here is an example:

Tables Review

Using Microsoft SQL Server Management Studio, to see the list of tables of a database using SQL, in a Query window, specify the database (using a USE statement), and execute sp_help (it is a stored procedure). Here is an example:

List of Tables

Private Sub Exercise_Load(ByVal sender As Object, _
                              ByVal e As System.EventArgs) _
                              Handles Me.Load
        Using connection As SqlConnection = _
  New SqlConnection("Data Source=(local);" & _
   "Database='AltairRealtors1';" & _
   "Integrated Security=yes;")
            Dim command As SqlCommand = _
         New SqlCommand("sp_help", connection)
            connection.Open()
            Dim rdr As SqlDataReader = command.ExecuteReader()

            While rdr.Read()
                lbxTables.Items.Add(rdr(0))
            End While

            rdr.Close()
        End Using
End Sub

sp_help

Renaming a Table

If you find out that the name of a table is not appropriate, you can change it. To change the name of a table in the SQL Server Management Studio, in the Object Explorer, right-click the table and click Rename. Type the desired name and press Enter.

To change the name of a table with code, execute sp_rename, followed by the current name of the table, a comma, and the new desired name of the table. The formula to use is:

sp_rename ExistingTableName, TableNewName;

The names of tables should be included in single-quotes. Here is an example:

sp_rename 'StaffMembers', 'Employees';
GO

In this case, the interpreter would look for a table named StaffMembers in the current or selected database. If it finds it, it would rename it Employees. If the table does not exist, you would receive an error.

Deleting a Table

If you have an undesired table in a database, you can remove it. To delete a table

  •  In the SQL Server Management Studio, in the Object Explorer, right-click the table under its database node and click Delete
  • In Microsoft Visual Studio, in the Server Explorer, expand the connection to the database that owns the table and expand its Tables node. Right-click the undesired table and click Delete

You will receive a warning giving you a chance to confirm your intentions. If you still want to remove the table, click OK.

To delete a table using SQL, use the following formula:

DROP TABLE TableName

The DROP TABLE expression is required and it is followed by the name of the undesired table. When you execute the statement, you will not receive a warning before the table is deleted.

You can also use sample code in Microsoft SQL Server Management Studio that can generate code for you. First display an empty query window. Also display the Templates Explorer and expand the Table node. Under Table, drag Drop Table and drop it in the empty query window. Sample code would be generated for you. You can then simply modify it and execute the statement.

Referring to a Table

In future lessons, we will write various expressions that involve the names of tables. In those expressions, you will need to specify a particular table you want to use. There are three main ways you can do this. To refer to, or to indicate, a table:

  • You can simply type its name. An example would be Students
  • You can type dbo, followed by the period operator, followed by the name of the table. An example would be dbo.Students
  • You can type the name of the database to which the table belongs, followed by the period operator, followed by dbo, followed by the period operator, and followed by the name of the table. An example would be RedOakHighSchool.dbo.Students
 

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