lession 7 records maintenance

Lecturer: Tran Dinh Vuong Home page: www.fit.vimaru.edu.vn/~vuongtd Phone : 0982.113.274 Email : [email protected]

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Lession 7: Records Maintenance

Data Import/Export

Data Import

One of the techniques used to get data into one or more tables consists of importing already existing data from another database or from any other recognizable data file. Microsoft SQL Server provides various techniques and means of importing data.

The easiest type of data that can be imported into SQL Server, and which is available on almost all database environments, is the text file. Almost every database environment allows you to import a text file but data from that file must be formatted appropriately. For example, the information stored in the file must define the columns as distinguishable by a character that serves as a separator. This separator can be the single-quote, the double-quote, or any valid character. Data between the quotes is considered as belonging to a distinct field. Besides this information, the database would need to separate information from two different columns. Again,

a valid character must be used. Most databases, including Microsoft SQL Server, recognize the comma as such a character. The last piece of information the file must provide is to distinguish each record from another. This is easily taken car of by the end of line of a record. This is also recognized as the carriage return.

These directives can help you manually create a text file that can be imported into Microsoft SQL Server. In practicality, if you want to import data that resides on another database, you can ask that application to create the source of data. Most applications can do that and format the data. That is the case for the data we will use in the next exercise: it is data that resided on a Microsoft Access database and was prepared to be imported in Microsoft SQL Server.

After importing data, you should verify and possibly format it to customize its fields.

Practical Learning: Importing Data From an External Source

1. Download the Students text file and save it to your hard drive

2. In the SQL Server Management Studio, right-click the Databases node and click New Database...

3. Type ROSH and press Enter

4. In the Object Explorer, right-click ROSH, position the mouse on Tasks and click Import

Data

5. On the first page of the wizard, click Next

6. On the second page, click the arrow of the Data Source combo box and select Flat File Source

7. On the right side of File Name, click the Browse button

8. Locate and select the Students.txt file you had saved

9. On the left side, click Columns

10. On the left side, click Advanced

11. As Column 0 is selected, in the right list, click Name and type StudentID

12. Click DataType and click the arrow of its combo box. Select Two-byte unsigned integer [DT_UI2]

http://functionx.com/sqlserver/Students.txt


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13. In the middle list, click each column and change its Name in the right column as follows:

Name DataType OutputColumnWidth

StudentID Two-byte unsigned integer [DT_UI2]

FirstName Unicode string [DT_WSTR] 20

LastName Unicode string [DT_WSTR] 20

DateOfBirth database date [DT_DBDATE]

Gender Unicode string [DT_WSTR] 12

Address Unicode string [DT_WSTR]

City Unicode string [DT_WSTR] 40

State Unicode string [DT_WSTR] 2

ZIPCode Unicode string [DT_WSTR] 12

HomePhone Unicode string [DT_WSTR] 16

EmailAddress Unicode string [DT_WSTR]

ParentsNames Unicode string [DT_WSTR]

SPHome Boolean [DT_BOOL]

EmrgName Unicode string [DT_WSTR]

EmrgPhone Unicode string [DT_WSTR] 16

14. To see the list of columns, under Data Source, click Columns

15. Click Next 3 times:


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16. Click Next twice

17. Click Finish


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18. Click Close

Record Maintenance: Updating Records

Introduction

Record maintenance includes viewing records, looking for one or more records, modifying one or more records, or deleting one or more records. These operations can be performed visually or programmatically using a Data Definition Language (DDL) command.

Practical Learning: Introducing Record Maintenance

1. On the Standard toolbar, click the New Query button

2. To create a database, type the following:

USE master;

GO

IF EXISTS(SELECT name

FROM sys.databases

WHERE name = N'CeilInn2'

)

DROP DATABASE CeilInn2

GO


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CREATE DATABASE CeilInn2

GO

USE CeilInn2;

GO

CREATE TABLE Rooms (

RoomID int identity(1, 1) NOT NULL,

RoomNumber nvarchar(10),

RoomType nvarchar(20) default N'Bedroom',

BedType nvarchar(40) default N'Queen',

Rate money default 75.85,

Available bit default 0

);

GO

INSERT INTO Rooms(RoomNumber) VALUES(104);

GO

INSERT INTO Rooms(RoomNumber, BedType, Rate, Available)

VALUES(105, N'King', 85.75, 1),

(106, N'King', 85.75, 1);

GO

INSERT INTO Rooms(RoomNumber, Available) VALUES(107, 1);

GO

INSERT INTO Rooms(RoomNumber, BedType, Rate)

VALUES(108, N'King', 85.75);

GO

INSERT INTO Rooms(RoomNumber, Available) VALUES(109, 1);

GO

INSERT INTO Rooms(RoomNumber, RoomType, Rate, BedType, Available)

VALUES(110, N'Conference', 450.00, N'', 1);

GO

3. Press F5 to execute

Visually Selecting Records

Before visually performing some operations on a table, you must first select one or more

records. In the Table window, to select one record, position the mouse on the left button of the record and click:

To select a range of records, click the gray button of one of the records, press and hold Shift, then click the gray button of the record at the other extreme.


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To select the records in a random fashion, select one record, press and hold Ctrl, then click the gray button of each desired record:

To select all records of a table, click the gray button on the left of the first column:

To visually modify one or more records on a table, first open it (you right-click the table in the Object Explorer and click Open Table) to view its records. Locate the record and the field you want to work on and perform the desired operation.

Updating all Records

Updating a record consists of changing its value for a particular column. To visually update a

record, in the Object Explorer, right-click its table (or view, in some cases) and click Edit Top 200 Rows. This would open the table as a spreadsheet, as seen above. Locate the value under the desired column header, and modify the value as you see fit.

To programmatically update a record, you use a Data Definition Language (DDL) command. If you are working in Microsoft SQL Server:

In the Object Explorer, you can right the table, position the mouse on Script Table As -> UPDATE To -> New Query Editor Window

Open an empty query window and type your code

The DDL command to update a record is UPDATE. The basic formula to use is:

UPDATE TableName

SET ColumnName = Expression

With this formula, you must specify the name of the involved table as the TableName factor of our formula. The SET statement allows you to specify a new value, Expression, for the field under the ColumnName column.

Consider the following code to create a new database named VideoCollection and to add a table named Videos to it:

CREATE DATABASE VideoCollection;


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GO

USE VideoCollection;

GO

CREATE TABLE Videos (

VideoID INT NOT NULL IDENTITY(1,1),

VideoTitle nvarchar(120) NOT NULL,

Director nvarchar(100) NULL,

YearReleased SMALLINT,

VideoLength nvarchar(30) NULL,

Rating nchar(6)

);

GO

INSERT INTO Videos(VideoTitle, Director, YearReleased, VideoLength)

VALUES(N'A Few Good Men','Rob Reiner',1992,'138 Minutes');

INSERT INTO Videos(VideoTitle, Director, VideoLength)

VALUES(N'The Lady Killers', N'Joel Coen & Ethan Coen', N'104 Minutes');

INSERT INTO Videos(VideoTitle, Director, YearReleased, VideoLength)

VALUES(N'The Silence of the Lambs','Jonathan Demme',1991,'118 Minutes');


VALUES(N'The Distinguished Gentleman', N'James Groeling', N'112 Minutes');


VALUES(N'Ghosts of Mississippi', N'Rob Reiner', N'130 Minutes');

GO

Imagine you want to indicate that all these videos are rated R. To do this, in our formula, specify the table name. In the SET expression, specify the column name as Rating and assign it R as a string. This would be done as follows:

USE VideoCollection;

GO

UPDATE Videos

SET Rating = N'R';

GO

If you use the UPDATE statement like this, it acts on all records. The above code would produce:

Record Maintenance: Editing Records

Introduction

Editing a record consists of changing a value in a field. It could be that the field is empty, such

as the © Year of the the 'The Lady Killers' video of the following table. It could be that the value


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is wrong, such as the Director of the the 'The Distinguished Gentleman' video of this table:

Video Title Director © Year Length Rating

A Few Good Men Rob Reiner 1992 138 Minutes R

The Silence of the Lambs Jonathan Demme 1991 118 Minutes

The Distinguished Gentleman James Groeling 112 Minutes R

The Lady Killers Joel Coen & Ethan Coen 104 Minutes R

Ghosts of Mississippi Rob Reiner 130 Minutes

Editing a Record

To edit a record, first open the table to view its records. Locate the record, the column on which

you want to work, and locate the value you want to change, then change it.

To edit a record, you must provide a way for the interpreter to locate the record. To do this, you would associate the WHERE operator in an UPDATE statement using the following formula:

UPDATE TableName


WHERE Condition(s)

The WHERE operator allows you to specify how the particular record involved would be identified. It is very important, in most cases, that the criterion used be able to uniquely identify the record. In the above table, imagine that you ask the interpreter to change the released year to 1996 where the director of the video is Rob Reiner. The UPDATE statement would be written as follows:

UPDATE Videos

SET YearReleased = 1996

WHERE Director = N'Rob Reiner';

In the above table, there are at least two videos directed by Rob Reiner. When this statement is executed, all video records whose director is Rob Reiner would be changed, which would compromise existing records that didn't need this change. This is where the identity column becomes valuable. We saw earlier that, when using it with the IDENTITYfeature, the interpreter

appends a unique value to each record. You can then use that value to identify a particular record because you are certain the value is unique.

Here is an example used to specify the missing copyright year of a particular record:

UPDATE Videos

SET YearReleased = 1996

WHERE VideoID = 5;

GO

Here is an example used to change the name of the director of a particular video:

UPDATE Videos

SET Director = N'Jonathan Lynn'

WHERE VideoTitle = N'The Distinguished Gentleman';

Practical Learning: Editing a Record

1. Press Ctrl + A to select everything (the code) in the window and, to update a record, type the following:

USE CeilInn2;

GO


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UPDATE Rooms

SET BedType = N'Queen'

WHERE RoomNumber = 108;

GO


3. Press Ctrl + A to select the code in the window and type the following:

USE CeilInn2;

GO

UPDATE Rooms

SET Available = 0

WHERE RoomNumber = 109;

GO


Outputting the Update

After making changes to a table using SQL, you don't get a visual display of what happened.

With Transact-SQL, you can temporarily display the result of this operation or you can store it in a table. We already saw how to do this when creating records. You follow the same formula when updating records. The formula is:

UPDATE TableName


OUTPUT INSERTED.Columns

VALUES(Value_1, Value_2, Value_X)

Besides the formula we have used so far, after the SET expression, start with an OUTPUTINSERTED expression, followed by a period. If you are to show all columns of the table, add the * operator. Otherwise, type INSERTED followed by a period, followed by the name of the column you want to show.

Practical Learning: Outputting the Update

1. Press Ctrl + A to select the code in the window

2. To update some records and show which ones were changed, type the following:

USE CeilInn2;

GO

UPDATE Rooms

SET Rate = 95.50

OUTPUT INSERTED.*

WHERE BedType = N'Queen';

GO


Record Maintenance: Deleting Records

Removing all Records

If you think all records of a particular table are, or have become, useless, you can clear the

whole table, which would still keep its structure. To delete all records from a table, first select all


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of them, and press Delete. You would receive a warning:

If you still want to delete the records, click Yes. If you change your mind, click No.

The DDL command to clear a table of all records is DELETE. It uses the following formula:

DELETE TableName;

When this statement is executed, all records from the TableName factor would be removed from

the table. Be careful when doing this because once the records have been deleted, you cannot get them back.

Removing a Record

If you find out that a record is not necessary, not anymore, or is misplaced, you can remove it from a table. To remove a record from a table, you can right-click its gray box and click Delete. You can also first select the record and press Delete. You would receive a warning to confirm your intention.

To programmatically delete a record:

In the Object Explorer, you can right the table, position the mouse on Script Table As ->DELETE To -> New Query Editor Window

Open an empty query window and type your code

In SQL, to delete a record, use the DELETE FROM statement associate the WHEREoperator. The formula to follow is:

DELETE FROM TableName

WHERE Condition(s)

The TableName factor is used to identify a table whose record(s) would be removed.

The Condition(s) factor allows you to identify a record or a group of records that carries a criterion. Once again, make sure you are precise in your criteria so you would not delete the wrong record(s).

Here is an example used to remove a particular record from the table:

DELETE FROM Videos


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WHERE VideoTitle = N'The Lady Killers';

Here is an example used to clear the table of all videos:

DELETE FROM Videos;

Outputting the Deleted Result

When some record(s) has(have) been deleted, the operation is performed behind the scenes and you don't see the result. If you want to see a list of the records that were deleted, you can use the OUTPUT operator to display the result. To show the list of the records from a table that was completely emptied, you can use the following formula:


OUTPUT DELETED.Columns

The OUTPUT INSERTED expression follows the description we have seen for the record update. Here is an example:

USE VideoCollection6;

GO

DELETE FROM Videos

OUTPUT deleted.*

GO

To show the list of the records that were deleted based on a condition, use the following formula:


OUTPUT DELETED.Columns

WHERE Condition(s)

Here is an example:

USE VideoCollection6;

GO

DELETE FROM Videos

OUTPUT deleted.*

WHERE YearReleased IS NULL;

GO

Practical Learning: Ending the Lesson

1. Close the query window without saving the file

2. In the Object Explorer, under the Databases node, right-click WorldStatistics and click Delete

3. In the dialog box, click OK

4. In the Object Explorer, under the Databases node, right-click CeilInn2 and click Delete

5. In the dialog box, click OK

Data Entry and Permissions

Introduction

As far as users are concerned, the primary reason for using a database is to open a table and use its records. You on the other hand need to control who has access to a table and what a

particular user can do on it. Fortunately, Microsoft SQL Server can let you control all types of access to the records of any table of your database. As seen for databases, you can grant or


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deny access to a table, to some users individually or to a group of users. Of course, you can work visually or programmatically.

Before exercising security on a table for a user, you must have created a user account for that user.

Managing Permissions on a Table

To visually grant or deny operations at the table level, in the Object Explorer, right-click the table and click Properties. In the Select a Page list, click Permissions. In the Users or Roles list, click the name of the user or click Select to locate the user. In the Permissions column, locate the type of permission you want. Manage the operations in the Grant and in the Deny columns.

In Microsoft SQL Server, every operation of a table has its own permissions:

More than on a database, the permissions of a table are very interconnected. This means that giving one type of access may not be enough to achieve the right result. This also means that you must know how to combine permissions:

ALTER: If this permission is granted, a user can open a table in design view and change its structure (design). For example, a person can add a new column or delete an existing column. In most cases, regular users should be denied this right

INSERT: This permission allows a user to create new records. If you don't want a user to


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add new records to the table, then deny this permission

UPDATE: This is one of the most important permissions when it comes to data entry

DELETE: This permission allows a user to delete one or more records. The reverse is to deny this right so the user can only see the records but cannot remove them

The basic formula to programmatically grant one or more permissions to a user is:

GRANT Permission1,Permission2, Permission_n

ON [ OBJECT :: ][ schema_name ].object_name [ (Column1, Column2, Column_n ] ) ]

TO Login1, Login2, Login_n ]

The basic formula to programmatically deny (a) permission(s) is:

DENY Permission1,Permission2, Permission_n

ON [ OBJECT :: ][ schema_name ].object_name [ (Column1, Column2, Column_n ] ) ]

TO Login1, Login2, Login_n ]

You start with the GRANT (or DENY) keyword. To grant a permission, type it. After specifying the types of permissions you want, type ON or ON OBJECT::. This is followed by the name of the object, that is, the table, on which you want to grant permissions. If necessary, or this is optional, precede the name of the object with the name of the schema. After the name of the object, type TO, followed by the login name that will receive the permission. Here is an example:

USE master;

GO

CREATE DATABASE Exercise1;

GO

USE Exercise1;

GO

CREATE TABLE Employees

(

EmployeeNumber nchar(10),

FirstName nvarchar(20),

LastName nvarchar(20),

);

GO

CREATE USER [Peter Mukoko]

FOR LOGIN rkouma;

GO

GRANT ALTER

ON OBJECT::Employees

TO [Peter Mukoko];

GO

If you want to combine permissions, separate them with commas. Here is an example:

USE Exercise1

GRANT INSERT, UPDATE

ON OBJECT::dbo.Payroll

TO [James Galvin];

GO

If you wan to grant the permission(s) to more than one account, separate them with commas.

Extending Permissions

As mentioned for a database, you can give one account the ability to grant or deny permissions

to other accounts. To do this visually, access the Database Properties for the database. In the


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Users or Roles section, select the user. In the Persmissions, use the check boxes in the With Grant column.

The formula to programmatically give an account the ability to grant or deny permissions to other accounts is:

GRANT Permission1,Permission2, Permission_n

TO Login1, Login2, Login_n

WITH GRANT OPTION

In this formula, you add the WITH GRANT OPTION expression.

lession 7 records maintenance

Education