SQL Database Development - Part II

About Tables

Tables Fundamentals A Computer Database is an application that contains one or more lists. A

list is a series of values. A simple list can be made of numbers. In a formal database, a list is called a table. In some documents, a tale is

called an entity. In some other documents, a table is referred to as a relation.

Introducing Tables:

Launch Microsoft SQL Server and connect In the Object Explorer, expand the Databases node if necessary.

In the Object Explorer, right-click Databases and click New Database... In the New Database dialog box, set the Database Name to University Click OK In the Object Explorer, right-click Databases and click Refresh Click the + button of University to expand it Under University, click the + button of Security to expand it Right-click Schemas and click New Schema... In the Schema Name text box, type Academics Click OK

Creating a TableOne way to create a table is to design it. To do this, in the Object Explorer, expand the Databases node and expand the database to which the table will belong. Right-click the Tables node and click New Table...

Creating a Table With SQL

To assist you with creating a table, the structured querylanguage, SQL, provides an operation, called a command, in its Data Definition Language (DDL). The command is CREATE TABLE and it is used is a formula that starts as follows:

CREATE TABLE TableName . . .The CREATE TABLE expression is required.TableName specifies the name of the new table.

Starting a Table

In the Object Explorer, under University1, right-click Tables and click New Table..

Temporary Tables

After creating a table, it becomes part of its database and you can use that table over and over again. In some cases, you may want to create a table to test something and you would not need to use that table the next time you connect to the server. Such a table is referred to as a temporary table.

To create a temporary table, use the pound sign, #, after CREATE TABLE. Once the table has been created, it would be available as long as you are using the same connection to the server. If you close Microsoft SQL Server, the table would be automatically deleted.

Primary Characteristics of a TableThe Name of a Table

When creating a table, you must give it a name. If you are visually creating a table, if you decide to close it, you would be asked whether you want to save it. If you click Yes, you would be asked to give it a name.

The name of a table:Can be made of digits only. For example you can have a table called 148Can start with a digit, a letter, or an underscoreCan 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 SecondAfter the first character as an underscore or a letter, 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

Because we consider that a table is a collection of values (a collection of records), the names of our table will be in plural (some people get very upset with it, just as some people make it a big deal that the name of a table be completely in uppercase). Examples are Customers or SeasonalEmployees

The Schema of a Table

As mentioned already, a schema is an object that contains other objects, such as tables. In fact, every table in Microsoft SQL Server must belong to a schema. When you are creating a table, you have the option of specifying or not indicating its schema. If you don't specify a schema, the default dbo schema would own it.

To visually specify the schema that will contain a table, in the Properties window, click Schema, then click the arrow of its combo box and select the desired schema:

To specify the schema of a table using code, precede its name with the name of the schema followed by a period. The formula to use is:CREATE TABLE SchemaName.TableName....An example would be:CREATE SCHEMA Registration; GO CREATE TABLE Registration.Students . . .

After creating a table, you can change its schema. To do this visually, open the table in Design view. In the Properties window, click the arrow of the Schema combo box and select the desired schema. You will receive a message box (based on the permissions):

If you still want to change the schema, click Yes.

Specifying the Schema of a Table If the Properties window is not visible, on the main menu, click View ->

Properties Window.While the table is displaying, in the Properties window, click Schema, then click the arrow of its combo box and select Academics

Tables MaintenanceIntroductionTable maintenance consists of reviewing or changing some of its aspects.

This includes reviewing the list of tables of a database, renaming a table, or deleting it.

Viewing the Properties of a Table 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 the Object Explorer, 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:

To view the structure of a table, perhaps to change its design, in the Object Explorer, expand your database and its Tables node. Right-click the table and click Design. 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

Modifying the Design of a Table

Probably the most routine operation you will perform on a table is to change its design. This is usually easily done after you have opened the table in Design view. You can then change what you want. After making the change(s), you must save the table. Depending on how your database is configured, you may receive an error as "Saving changes is not permitted...":

To avoid the below error and make it possible to modify tables, on the main menu of SQL Server Management Studio, click Tools -> Options... In the left tree list of the Options dialog box, click Designers. In the Table Options, clear the Prevent Saving Changes That Require Table Re-Creation check box.

Allowing Changes on TablesOn the main menu of SQL Server Management Studio, click Tools ->

Options... In the left tree list of the Options dialog box, click Designers In the Table Options, clear the Prevent Saving Changes That Require Table

Re-Creation check boxClick OK

Tables ReviewTo see the list of tables of a database in the Object Explorer, you can click the Tables node:

To see the list of tables of a database using SQL, in a Query Editor, specify the database (using a USEstatement). On the next line, type sp_help and execute it. Here is an example:

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, typesp_rename, followed by the current name of the table, a comma, and the new desired name of the table. Then execute the code. 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 N'StaffMembers', N'Employees'; GO In this case, the database engine 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 doesn't 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. You will receive a warning giving you a chance to confirm your intentions. If you still want to remove the table, click O

To delete a table using SQL, use the following formula:DROP TABLE TableNameThe 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 that Microsoft SQL Server can generate for you. First display an empty Query Editor. Also display the Templates Explorer and expand the Table node. Under Table, drag Drop Table and drop it in the empty Query Editor. Sample code would be generated for you. You can then simply modify it and execute the statement.

Referring to a Table

In your database development assignments, you will write 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 StudentsYou can type the schema name, followed by the period operator, followed

by the name of the table. An example would be Registration.Students. In reality, if a table belongs to a schema other thandbo, you should always precede its name with its schema

You can type the name of the database to which the table belongs, followed by the period operator, followed by the schema, followed by the period operator, and followed by the name of the table. An example would be RedOakHighSchool.Registration.Students Continue….

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