INTRODUCTION MySQL is a key part of LAMP (Linux, Apache, MySQL, PHP / Perl / Python), the fast-growing open source enterprise software stack. More and more companies are using LAMP as an alternative to expensive proprietary software stacks because of its lower cost and freedom from platform lock-in. MySQL was originally founded and developed in Sweden by two Swedes and a Finn: David Axmark, Allan Larsson and Michael "Monty" Widenius, who had worked together since the 1980's.
TO LOGIN To login (from unix shell) use -h only if needed.the command used to login is [mysql dir]/bin/mysql -h hostname -u root -p
DDL COMMANDS DDL is abbreviation of Data Definition Language. It is used to create and modify the structure of database objects in database. Examples: CREATE, ALTER, DROP statements
CREATE Creates objects in the database the queery used to create theobject is create database [databasename]; Example : create database [employee];
ALTER Alters objects of the database ALTER TABLE <table_name> ADD <column_name1> <datatype1> <constraint1> ALTER TABLE <table_name> ALTER COLUMN <column_name1> <datatype1> <constraint1> ALTER TABLE <table_name> DROP COLUMN <column_name1> <datatype1>
DROP Deletes objects of the database the syntax for dorp is DROP TABLE [ IF EXISTS ] table_name1, table_name2, .... Removes the table(s) from the database. The IF EXISTS clause will drop the table only if it exists. If this clause is not present an error is generated if the table does not exist. Any data that was in a dropped table is lost so use with care.
DML COMMANDS DML is abbreviation of Data Manipulation Language. It is used to retrieve, store, modify, delete, insert and update data in database. Examples: SELECT, UPDATE, INSERT statements
SELECT SELECT [ DISTINCT | ALL ] column_expression1, column_expression2, .... [ FROM from_clause ] [ WHERE where_expression ] [ GROUP BY expression1, expression2, .... ] [ HAVING having_expression ] [ ORDER BY order_column_expr1, order_column_expr2, .... ] The SELECT statement is used to form queries for extracting information out of the database. The following example query will return the number, quantity and price of all orders for more than 5 items sorted in descending order by order number. to the output.
UPDATE UPDATE table_name SET col_name1 = expression1, col_name2 = expres sion2, .... [ WHERE expression ] [ LIMIT limit_amount ] Updates information in a table. The SET clause is a list of assignments that describe how the columns of the data matched by the WHERE clause are to be updated.
INSERT INSERT INTO table_name [ ( col_name1, col_name2, .... ) ] VALUES ( expression1_1, expression1_2, .... ), ( expression2_1, expression2_2, .... ), .... This is the SQL command to insert records into a table in the database. This statement comes in three forms.
The Second form of insert command INSERT INTO table_name [ ( col_name1, col_name2, .... ) ] SELECT ... The Third form of insert cmmand INSERT INTO table_name SET col_name1 = expression1, col_name2 = expression2, ....
TCL COMMSNDS TCL is abbreviation of Transactional Control Language. It is used to manage different transactions occurring within a database. Examples: COMMIT, ROLLBACK statements
COMMIT AND ROLLBACK Saves work done in transactions The Syntax COMMIT ROLLBACK Transactional operations for closing a transaction and either committing all the changes made or rolling back and disposing all changes
DCL COMMANDS DCL is abbreviation of Data Control Language. It is used to create roles, permissions, and referential integrity as well it is used to control access to database by securing it. Examples: GRANT, REVOKE statements
GRANT AND REVOKE GRANT privileges ON database_object TO ( PUBLIC | user_list ) [ WITH GRANT OPTION ] REVOKE [ GRANT OPTION FOR ] privi- leges ON database_object FROM ( PUBLIC | user_list ) Grants or revokes types of access on a table or view to a user. When a table or view is created the system gives full grant options to the user that created the object.
OTHER COMMANDS SET SET variable = expression SET AUTO COMMIT ( ON | OFF ) SET TRANSACTION ISOLATION LEVEL ( SERIALIZABLE ) SET SCHEMA schema_name Makes a change to the state of the connection. SET AUTO COMMIT is used to switch transaction 'auto commit mode' on or off.
DESCRIBE SYNTAX DESCRIBE table_name This command provides information about the columns of the table. It shows the column names, the type / size and scale (if applicable) and other useful information.
SHOW SHOW engine_variable engine_variable ::= TABLES | SCHEMA | STATUS | CONNECTIONS Shows internal information about the database system. SHOW TABLES returns a list of tables in the database. SHOW STATUS returns debugging and statistical information about the internal state of the database engine. SHOW CONNECTIONS returns a snapshot of the current connections on the database. SHOW SCHEMA lists all the schema defined.
SHUTDOWN SYNTAX SHUTDOWN Shuts down the database. If the database is running as a server the database shuts down cleanly and the process is stopped. If the database is embedded in a Java application it is cleanly put into a shut down state.