MySQL Basics

OVERVIEW OF MYSQLwhat is mysql?Where to download mysql?What is database?What is sql?Basic queries in mysql?

MYSQLMysql is the most popular open source database system Mysql is a relational databasemanagement system It is a free SQL server database server licensed with GNU www.gnu.org

STEPS TO DOWNLOAD MYSQL1.goto www.mysql.com2.click on downloads3.choose the host operating system4.download and run mysql5.go back and click on gui tools6.download and run mysql gui tools

DatabaseData: known facts that can be recorded and that have implicit meaningDatabase: collection of related data.It is a logical collection of coherent data with some inherent meaning.DBMS: A computerised record-keeping system.

Goals of a DBMS:To provide an efficient and convenient environment for accessing data in dbIt is a general purpose facility for:Defining dbConstructing dbManipulating db

SQL-structured query languageSQL is now the standard language for commercial relational DBMS.It has statements for data definitions, queries and updates.

START MYSQL SERVER:log in as root under linux with the command safe_mysqld &1) without any password:mysql -u <user> -h <host>2)with password:mysql -u <user> -h <host> -p ex: mysql –u root –h localhostdesc: -u option is used to log in as a root and –p option tells mysql to query for the password.

BASIC QUERIES IN MYSQL1.CREATE TABLE create table table_name(column1 data type(NULL||NOT NULL);desc: creates a table.2.SHOW table show CREATE TABLE table_name;desc: shows the table in your database.

3.INSERT insert into table_namevalues[‘value1’,’value2’,……..);desc: inserts new rows of data into the database.4.SELECTselect * from table table_name.desc: returns data from the table.

5.SELECTselect column1,column2,…from table1,table2,….[where conditions][group by column1,column2,..][having conditions][order by column1,column2,…]desc: returns data from one or more database tables.

6.UPDATEupdate table_name set column1=‘value1’,column2=‘values’,…[where conditions]desc: updates existing data in the table.7.DELETEdelete from table_name[where conditions]desc: deletes rows of data from a table.

Mysql classes1.SELECTselect *select col1,col2,…select distinct(column)select count(*)desc: defines columns to display as part of query output.

2.FROMfrom table1,table2,table3,..Desc: defines tables from which to retrieve data.3. GROUP BYgroup by grp_col1,grp_col2,…desc: a form of a sorting. Used to divide output into logical groups.

4.HAVINGhaving grp_col1=‘value1’AND grp_col2=‘value2’desc: similar to the where clause, used to place conditions on the group clause.5.ORDER BYorder by col1,col2,…desc: used to sort a query’s result.

mysql functions:1.rand()desc: returns random values2.sum()desc: returns the sum of the values.3.now()desc: returns the time and date of the system.4.count()desc: returns the count of the values which satisfy the given condition.

sample code to create a table employee and run basic queries using mysql on windows operating system:Mysql>create table employee(Ssn INT NOT NULL,Salary INT,Name VARCHAR(20)Department VARCHAR(20),Primary key(ssn));Query ok, 0 rows affected (0.04 sec)

Mysql>insert into employeeValues(100,10000,’sneha’,’finance’);Query ok, 1 row affected(0.04 sec)Mysql>insert into employeeValues(200,20000,’shalini’,’hr’);Query ok, 1 row affected(0.04 sec)

Mysql>insert into employeeValues(300,30000,’john’,’finance’);Query ok, 1 row affected(0.04 sec)Mysql>insert into employeeValues(400,40000,’jack’,’hr’);Query ok, 1 row affected(0.04 sec)

Mysql>select * from employee;

Mysql>select department, count(*) as number from employee group by department order by number desc;

Mysql>show create table employee;

Mysql> select name, ssn from employee order by ssn desc limit 2;

Mysql>update employee set salary=9000 where ssn=400;Mysql>select * from employee;

Mysql>delete from employeewhere name=‘jack’;mysql>select * from employee;

Mysql>drop table employee;query ok, 0 rows affected (0.04 sec)Mysql>select * from employee;ERROR 1146 (42S02): Table ‘mysql.employee’ doesn’t existuse quit or exit to come out of mysql.Mysql>quit

Advantages of mysql:1.Its most reliable.2.Easy to use.3.Very fast.4.Multithreadedmulti-user and5.Robust sqldatabase server.

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MySQL Basics

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MySQL Basics