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Information backups are extremely simple to recognize. However, the implementation and storage components come with a challenging edge for every website hosting organization. Numerous third party backup mechanisms are known and currently being found out now. However one of the most preferred amongst them continues to be the MySQL instrument.

The MySQL in database server can get ruined in a a great number of methods regardless of how excellent a piece of application and just how skilled the end users may possibly be. Finding back the MySQL is far from a difficult thing if you’re obtaining trusted backups in place.

InnoDB is well-known since the main storage engine for MySQL. InnoDB includes an automatic embedded recovery program that features pretty seamlessly. At any point when the database hosting is snapped, InnoDB involves rescue and attempts repairing challenge by working the log file from the obtainable previous timestamp. In practically every instance the InnoDB meets with achievement. Unusual ailments like operating technique failures or energy crashes offer you examples where monotonous data recovery is carried out by InnoDB. In contrast if and when there exists failure of InnoDB in supplying automatic restore solution, the complete database will get paralyzed.

No a lot less major for just about any hosting organization would be the proven fact that regular and timely backups of one’s database should be scheduled. The mysqldump utility for conducting backups of data being a snapshot with reference to some level of time can be a really crucial instrument. The administrators keep to the beneath command to produce a “dump file” of MySQL database:

shell> mysqldump –single-transaction –flush-logs –master data=2 \

–all-databases > dump.sql

You are able to go ahead and name the output file in any way you make sure you – in the present-day scenario it is actually titled dump.sql. This dump.sql file is made of the information, structures of all databases & tables entirely backed up into an SQL text file, called the dump.sql.

While in the aforementioned command, ‘-single-transaction element is mainly for InnoDB tables. It executes an online backup that allows no locks on tables.

It is actually crucial that you duly save incremental changes so as to be able to find incremental backups- incredibly crucial for website hosting companies. By using binary logs, this step can be easily achieved. It is actually advisable to start MySQL always with the -log-bin option to enable that binary log. While in the mysqldump command mentioned here above you can see the ‘-flush-logs’ option using which administrators can flush out various logs. A proper flushing schedule of such logs can be kept to ensure it really is carried out on incremental basis during dump backups to sustain full data changes initiated since the time of initial backups.

Imagine you have a case in which your database goes through a devastating crash. Restoring operations become simplified if typical backups are organized along with binary logs. In this case it can be advised to take restore till the point of previous overall backup through the under command:

shell> mysql < dump.sql

Now you get data restored to the point it was when you did last mysqldump backup. For restoring different changes that may have accrued since then, always take incremental backups from binary log files that you find listed in the data directory of MySQL server (in this example, logfilename-bin.000001 and logfilename-bin.000002).

shell> mysqlbinlog logfilename-bin.000001 logfilename-bin.000002 | mysql

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Implementing Database in MySQL – Part 9

Introduction
This is part 9 of my series, Implementing Database in MySQL. I assume you have read all the different parts of the series (or equivalent tutorials from elsewhere) up to this point. In this part of the series, we see how to manipulate data in a MySQL. Remember we are dealing with MySQL 5.1

Note: If you cannot see the code or if you think anything is missing (broken link, image absent), just contact me at forchatrans@yahoo.com. That is, contact me for the slightest problem you have about what you are reading.

Data Manipulation
Data manipulation in database means to insert data rows into a table, update (modify the data) the rows and to delete the rows.

Inserting a Row
To insert a row of data, you have to be connected to the database first, and you need to have been given the permission to do that. In simple terms, the syntax is:

INSERT INTO table-name (column-name, column-name, column-name, …) VALUES (value, value, …)

A string value should be in quotes (single quotes). We shall put in values into the Products table of the wholesale database.

– Start and connect to the server and choose the wholesale database with the following commands:

cd c:\
“C:\Program Files\MySQL\MySQL Server 5.1\bin\mysql” -u root -p
Enter password: sql
USE wholesale;

– Read and type the following commands at the mysql prompt; avoid making a mistake (maybe you can copy and paste) pressing the Enter key just after the semicolon of each SQL statement;

INSERT INTO Products (ProductName, Category, Quantity, ReorderLevel, CostPrice, SellingPrice) VALUES (‘Pen’, ‘Office’, ’300′, 25, ’0.5′, ’0.75′);
INSERT INTO Products (ProductName, Category, Quantity, ReorderLevel, CostPrice, SellingPrice) VALUES (‘Books’, ‘Office’, ’500′, 30, ’3′, ’4′);
INSERT INTO Products (ProductName, Category, Quantity, ReorderLevel, CostPrice, SellingPrice) VALUES (‘Bowl’, ‘Household’, ’400′, 35, ’2′, ’3′);
INSERT INTO Products (ProductName, Category, Quantity, ReorderLevel, CostPrice, SellingPrice) VALUES (‘Spoon’, ‘Household’, ’350′, 40,  ‘.1′, ‘.2′);
INSERT INTO Products (ProductName, Category, Quantity, ReorderLevel, CostPrice, SellingPrice) VALUES (‘Plate’, ‘Household’, ’450′, 45, ’1′, ’1.25′);

Any SQL statement must end with a semicolon. You should have a positive feedback for any row inserted. Note that the ProductID column is autonumber and so it is not in the INSERT statements. The money is in dollars, but the dollar sign is not type. Amount given is for unit price.

You must be given the permission to update a row in a table before you can do so. You could insert the above rows since you are the DBA. You must also be given the permission to insert or delete a row in a table. As DBA that you are, you will be able to do these as shown below.

Updating a Table
To update a table means to modify the rows. We shall modify just one row in the Products table. We shall change the string, “Office” in the Category column to “School” in the second row of the table, where the ProductID is 2.

A simplified syntax for the UPDATE SQL Statement is:

    UPDATE table-name SET column-name = value WHERE search-condition;

The words in uppercase are reserved words. We want to set Category (column) to “School” where ProductID = 2.

– So, read, type and execute (press Enter) the following Update SQL statement:

    UPDATE Products SET Category = ‘School’ WHERE ProductID = 2;

You should have a positive feedback. In the statement, UPDATE, SET and WHERE are reserved words.

Deleting Rows
Let us delete the fourth row of the Products table, where the ProductID = 4. A DELETE simplified SQL syntax is:

DELETE FROM table-name WHERE search-condition;
   
DELETE means delete at least one row. We want to delete from the table, Products, where ProductID =ń.

– So, read, type and execute the following SQL statement:

DELETE FROM Products WHERE ProductID = 4;

You should have a positive feedback. Note: when an autonumber such as 4 above is deleted, it is generally not replaced the next time you add (insert) rows into the table. Assume that you insert a new row to the above table using the INSERT statement as above, the new autonumber will be 6 and not 4.

– Now, drop the connection, stop the database, and stop the server with the following command:

QUIT

That is it for this part of the series. Let us stop here and continue in the next part.

Chrys

To arrive at any of the parts of this division, type the corresponding title below in the search box of this page and click Search (use menu if available).

Implementing Database in MySQL – Part 1
Implementing Database in MySQL – Part 2
Implementing Database in MySQL – Part 3
Implementing Database in MySQL – Part 4
Implementing Database in MySQL – Part 5
Implementing Database in MySQL – Part 6
Implementing Database in MySQL – Part 7
Implementing Database in MySQL – Part 8
Implementing Database in MySQL – Part 9
Implementing Database in MySQL – Part 10
Implementing Database in MySQL – Part 11
Implementing Database in MySQL – Part 12
Implementing Database in MySQL – Part 13
Implementing Database in MySQL – Part 14
Implementing Database in MySQL – Part 15
 

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Database Table Data Types
Database Essentials – Part 3
Division 1

Introduction
This is part 3 of my series, Database Essentials. Database Essentials is division 1 of a set of tutorials I have on Database. Data Types also known as Data Domains refers to the kind of data that goes into a column of a table. In this part of the series we look at database Data Types. If the values of a column are whole numbers then the data type of that column is integer. If the values of a column are strings then the data type for that column is text. There are other data types; we look at them in this part of the series.

Byte and Kilo
The length of a message is measured in bytes. One byte is one character. Kilo abbreviated K in computer software is 2 raise to the power 10.

Implementation
After designing the tables for a database, you need to code it (implement it) in a database management system. There are many DBMS. They come in different software packages such as Microsoft Access, Oracle, MSSQL, MySQL, Sybase, etc. The data types I describe to you in this tutorial are those of Microsoft Access. Those for the other packages are similar. When you are creating a table in a DBMS you have to specify the data type for each column in the table.

Text
This refers to phrase composed of letters and/numbers. This data type can be used for an address column for example. It can also be used for a column that has numbers that do not require calculations. Examples of sets of numbers that are not used for calculation are phone numbers and postal code. If you have a column in a table for phone numbers or postal code, its data type should be text. An example of a set of numbers that is used in calculation is money figures. The maximum size of the text data type is 255 bytes. So, if you declare a column as having a data type of text, none of its cell content should be longer than 255 bytes.

Memo
This data type is used for lengthy text (which may include numbers). You can use this data type for columns that have notes or descriptions. The maximum size for this data type is Ƞ,000 characters.

Integer
This is a whole number data type. You use this data type for a column that has whole numbers. If you have a drinking bar for example, you may be interested in the number of bottles of drinks bought each day. You might have a database table, which has a column with the name, noOfDrinks; each row in such a table can represent a day’s information. So each table cell for the noOfDrinks column will have a whole number, for number of drinks sold on a day.  An integer can be up to 2 bytes long.

Floating
The integer data type takes only whole numbers. A whole number does not have a fractional part. If you would use numbers with fractional parts then you need the Floating data type. The floating data type accepts numbers with fractional parts. However, the fractional part has to be in decimal. Examples of floating numbers are: 23.758, ጤ.4, and 589652.7454. This kind of numbers cannot be put in table cells whose column has been declared to have integers; you have to put them in cells whose column has been declared to have floating numbers.

Currency
Currency is a data type. This is for money. You can have a table column for money. There are many currencies in the world. Dollar and Euro are examples. The currency data type can be up to 8 bytes long. You may wonder why the floating data type is not used for currency. The reason is that money values are usually large (large whole number part) and need more precision. For example, accountants in the bank work with a lot of money number precision. They do not want any one penny to be unaccounted for.

Date/Time
Date/Time is a data type. An example of a date is 02-04-2009. There is more to the Date/Time data type. Read the documentation of the particular DBMS to know exactly how you have to type or input the date and/or time. The Date/Time data type can be up to 8 bytes long.

Boolean
With this data type a cell of a column can have either “true” or “false”. A data type is specified for a column (not for a row). Some DBMS may take “yes” for true and “no” for false or “on” for true and “off” for false. The Boolean data type is known to have a size of one bit.

AutoNumber
This data type is typically used for a surrogate key that we saw in the previous part of the series. The difference between consecutive numbers in the cells of the column of this data type is 1 unit. Any of these numbers can be up to the size of 16 bytes.

BLOB
This data type is used for files. Have you ever imaging that files can be stored in a database? You can have one column in a table and each cell in the column will hold a file. What are files? You already know them. When you type a document in a word processor or text editor and save the document, the saved document is a file. Each image you see on a web page on the Internet is stored as a file in the hard disk of an Internet server. There are all kinds of files. Some files are executable files, in the sense that when you double click their icons within the operating system, they perform some task.

The BLOB data type is used to store any of these files; that is the BLOB data type is meant for storing files. It is the code of the file that is stored in a database table cell. The database itself cannot use the file. If the file is to be used, a copy of it has to be sent to some application, such as the one (word processor) that was used to create the file.

BLOB stands for Binary Large OBjects. This data type is used for storing files. If you declare a column of a database table to have the data type BLOB, then each cell of the column will be able to hold the code of a file.

Actually the BLOB data type is used for holding anything that is large in code form, which the DBMS does not really use. The DBMS can use numbers in a number column to find averages and totals, but is not expected to use the cell contents of the BLOB types to do anything.

Table Column Design Worksheet
For every table in the database there has to be a Table Column Design Worksheet. The Table Column Design Worksheet is not a table that holds data. It holds information about the data table itself. You will have to open the following link in your browser window tab to see an example.

        http://www.cool-mathematics.com/diagrams/design-worksheet-table.htm

The Table Column Design Worksheet has rows. Each of the rows gives information about a column in the data table. In the browser window tab you have opened, Table 3.1 shows an employee table. The diagram below shows the Table Column Design Worksheet for the employee table. Employee table is the data table.

In the Table Column Design Worksheet there should be at least three columns. There is first off all the entity name and the table name. The entity name is just the name the users have for the table. The table name is the database table name, which is the name you will use in the implementation (coding). Both the entity and table name can be the same.

The first column in our Table Column Design Worksheet lists the data table column names. The second column gives the data type for each column in the data table. The third column gives the description of each column in the data table. For this third column, where the name of the column of the data table is explicit (e.g. LastName), the description is not given.

Table Column Design Worksheet does not have to be coded with the database during implementation. You can have it in a notebook (paper book) in your office. However, some people create separate database tables during the implementation phase in the DBMS for the Table Column Design Worksheets for each of the data tables of the database. Remember, the data tables, which are the database tables (e.g. employee) will be coded in the DBMS during implementation.

For the Table Column Design Worksheet of the employee table, only the AutoNumber and the Text data types feature. This is alright; all the data types do not have to feature in a Table Column Design Worksheet. The data types that feature, depend on the actual data table columns data. If we had something like a Date_Hired column in the employee table, then the Date/Time data type would have featured in the Table Column Design Worksheet. Pictures are stored in the computer in files: one picture as a file. If we had a column for employee pictures in the employee table, then the BLOB data type would have been used in the employee table. The employee table would have a column whose cells have the code files for each of the employee picture. The Table Column Design Worksheet would also have a corresponding row with the data type, BLOB. In the case of pictures, the user would need a program that would decode the code files for the pictures in order to see the pictures.

That is what I have for you for this tutorial. Let us end here and continue in the next part of the series.

Chrys

To arrive at any of the parts of this series, just type the corresponding title below and my name, Chrys, in the Search Box of this page and click Search (use menu if available):

Database
Database Table Keys
Database Table Data Types
Database Associations Overview
Database N-to-N Relationships
Database N-ary Association
Aggregation Association
Composition Association
Generalization Association
Reflexive Association
Computed Values
Database Events
 

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