mysql

• The key to organizational success is effective decision making which requires timely, relevant and accurate information.
• Database Management Software (DBMS) simplifies the task of managing the data and extracting useful information out of it.
• Data is a collection of raw facts which have not been processed to reveal useful information.
• Information is produced by processing data as shown in Figure 1.2(a).
• Given the data of the test marks of all the students in a class, the average, maximum and minimum marks in the class can be used as indicators of the performance of the class.
• Examples of DBMS include MySQL, Oracle, DB2, IMS, IDS etc.
• DBMS is used by different types of users such as end users, database administrators, application programmers, and system analysts.
• The main characteristics of a DBMS are: self-describing nature of a database system, insulation between programs and data, sharing of data, and concurrency control software.
• The various operations that need to be performed on a database are: defining the database, populating the database, manipulating the database, sharing the database, protecting the database, and maintaining the database.
• The advantages of using a DBMS include reduction in redundancy, improved consistency, improved availability, improved security, and user friendliness.
• Databases are used extensively in business, engineering, medicine, education, library, to name a few.
• A database is a collection of related data that has been recorded, organized and made available for searching.
• A database has the following properties: it is a representation of some aspect of the real world, it is designed, built and populated with data for specific purpose, it can be of any size and complexity, it can be maintained manually or it may be computerized.
• The difference between the two queries is in the use of asterisk (*) symbol which is used to count the number of rows in the result of the query.
• A Select command can also result in an empty set, for example, retrieve the name of Teacher with ID=115.
• The query to retrieve the number of teachers in “Computer Science” Department can be written as follows: SELECT COUNT(*) AS No_of_Computer_Science_Teachers FROM Department, Teacher WHERE Dept_Name = "Computer Science" AND Dept_No=Dept_ID.
• It is also possible to apply some condition on the group, which will not come under the WHERE clause, but in a new clause HAVING.
• The attribute used for grouping ( Dept_No in the above query) must also be present in the SELECT clause.
• The maximum salary in the Teacher table is 54000 and the minimum salary is 34000.
• The query to count the number of teachers earning more than Rs 40000 can be written as follows: SELECT COUNT(Salary) FROM Teacher WHERE Salary > 40000.
• The SELECT statement can be enhanced by displaying the name of Departments also as shown below: SELECT Dept_No, Dept_Name, COUNT(*) AS No_of_Teachers FROM Teacher, Department WHERE Dept_ID = Dept_No.
• In traditional file processing, data is stored in the form of files and different application programs are written by programmers to insert, delete, modify and retrieve data from these files.
• In MySQL server 5.6.20, the CASCADE and RESTRICT options are not supported for the Drop Table command.
• The foreign key TEACHER_FK in the Teacher table can be dropped using the ALTER TABLE command.
• The command to drop a table is DROP TABLE Teacher CASCADE; which drops the table and all the constraints that refer to it.
• The command to drop named constraints is DROP TABLE Teacher RESTRICT; which can be used along with the Alter Table command.
• A column can be dropped from a table using the ALTER TABLE command.
• A column can be added to a table using the ALTER TABLE command.
• The Drop Table command in MySQL server 5.6.20 does not allow to drop a table if it is being referenced in other tables.
• The ALTER TABLE command is used to add, drop, or alter columns in a table.
• The primary key constraint in a table is named as TEACHER_PK and the foreign key constraint is named as TEACHER_FK.
• A constraint can be named by using the keyword CONSTRAINT followed by the name of the constraint and its specification.
• A foreign key/primary key/key can be dropped by using the ALTER TABLE command.
• The ALTER TABLE command can be used to alter the column definition, for example, to drop the default value or to define a new default value.
• The CASCADE and RESTRICT options are not supported in MySQL server 5.6.20 for the Drop Table and Alter Table commands.
• The GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users.
• The General Public License is designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change software or use pieces of it in new free programs; and that you know you can do these things.
• Before continuing, the Installer will determine if updates are available for the products you are about to install or upgrade.
• The MySQL Installer guides you through the installation and configuration of your MySQL products.
• The GNU General Public License Version 2, June 1991, applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it.