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Ddl commands

Ddl commands






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    Ddl commands Ddl commands Document Transcript

    • A. DDL Commands on MySQL: Create a databaseCreate database [database name]; To delete a db.Drop database [database name]; To delete a table.Drop table [table name]; Delete a column.Alter table [table name] drop column [column name];ALTER TABLE employee DROP INDEX name_dept; - get rid of Add a new column to db.Alter table [table name] add column [new column name] varchar (20);ALTER TABLE employee ADD EmpId INT NOT NULL AUTO_INCREMENT PRIMARYKEY; Change column name.Alter table [table name] change [old column name] [new column] varchar (50); Make a unique column so you get no dupes.Alter table [table name] add unique ([column name]); Make a column bigger.
    • Alter table [table name] modify [column name] varchar (3); Delete unique from table.Alter table [table name] drop index [column name]; Delete data from specific fields within a column:Mysql> DELETE FROM mytable WHERE mycolumn="mydata"; Rename a table within a specific databaseMysql> RENAME TABLE first TO second;(Or)Mysql> ALTER TABLE mytable rename as mynewtable; Create Table Example 1.Create table [table name] (first name varchar(20),middleintial varchar(3),lastname varchar(35),suffix varchar(3),officeid varchar(10),useridvarchar(15),username varchar(8),email varchar(35),phone varchar(25),groupsvarchar(15),datestamp date,timestamp time,pagemail varchar(255));CREATE TABLE pet (name VARCHAR(20), owner VARCHAR(20), speciesVARCHAR(20), sex CHAR(1), birth DATE, death DATE);CREATE TABLE retired_employee (Name char(20) DEFAULT NOT NULL,Deptchar(10) DEFAULT NOT NULL,JobTitle char(20)UNIQUE name_dept(Name,Dept));CREATE UNIQUE index name_dept on employee (name,dept); - avoids duplicatekeys Create Table Example 2.Create table [tablename] (personid int(50) not null auto_increment primarykey,firstname varchar(35),middlename varchar(50),lastname char(50) default‘bato’;
    • Create table employees (employee_id integer, first_name varchar (20), last_nameVarchar (20)) type=MyISAM; Drop DatabaseDrop database databasename; Delete a row(s) from a table.DELETE from [tablename] where [fieldname]=’whatever’; DROP TABLEDROP TABLE TABLENAME; Simple column and field manipulationShow columns within a table:Mysql> DESC mytable;(Or)Mysql> SHOW COLUMNS FROM mytable;B. DML Commands : Show all data in a tableSELECT * FROM [TABLENAME]; Show certain selected rows with the value “whatever”SELECT * FROM [tablename] where [field] =”whatever”; Show all records containing the name "Bob" AND the phone number 3444444.SELECT * FROM [TABLENAME] WHERE NAME=”bob” ANDphone_number=’3444444’;
    •  Show all records not containing the name "Bob" AND the phone number3444444 order by the phone_number field.SELECT * FROM [TABLENAME] WHERE NAME! =”bob” andphone_number=’3444444’ order by phone_number; Show all records starting with the letters bob AND the phone number 3444444.SELECT * FROM [TABLENAME] WHERE NAME LIKE “bob%” andphone_number=’3444444’; Show all records starting with the letters bob AND the phone number 3444444limit to records 1 through 5.SELECT * FROM [TABLENAME] WHERE NAME LIKE “bob%” andphone_number=’3444444’ limit 1,5; Use a regular expression to find records. Use "REGEXP BINARY" to force case-sensitivity. This finds any record beginning with a.SELECT * FROM [TABLENAME] WHERE rec RLIKE “^a”; Show unique records.SELECT DISTINCT [column name] FROM [TABLE NAME]; Show selected records sorted in an ascending (asc) or descending (desc).Select [col1], [col2] from [tablename] order by [col2] desc; Return number of rows.SELECT COUNT (*) FROM [TABLENAME]; Is there a way to query the DB to find out how many rows there are in all thetables?SELECT TABLE_NAME, TABLE_ROWS FROM `information_schema`.`tables` WHERE`table_schema` = mrsqa4;
    •  Is there a way to get the count of rows in all tables in a mysql database withoutrunning a SELECT count () on each table?SELECT SUM (TABLE_ROWS) FROM INFORMATION_SCHEMA.TABLESWHERETABLE_SCHEMA = mrsqa4; Sum column.SELECT SUM (*) FROM [TABLENAME]; Show the last 200 queries to your database with the sample table name "queries"and the sample field "query_id"Mysql> SELECT * FROM queries ORDER BY query_id DESC LIMIT 200; Show data within a specific table in a previously selected databaseMysql> SELECT * FROM table name; Select data within a specific table in a previously selected database:Mysql> SELECT * FROM mytable WHERE mycolumn=mydata ORDER BYmycolumn2; Join tables on common columns.Select lookup.illustrationid, looup.personid,person.birthday from lookupLeft join person on lookup.personid=person.personid=statement to joinBirthday in person table with primary illustrationid;MySQL> SELECT DISTINCT dept FROM bedrock;MySQL> SELECT * FROM pet WHERE species = "snake" OR species = "bird";MySQL> SELECT * FROM pet WHERE species = "dog" AND sex = "f";MySQL> SELECT * FROM pet WHERE birth >= "1998-1-1";MySQL> SELECT name, birth FROM pet ORDER BY birth DESC;MySQL> SELECT * FROM pet WHERE name LIKE "b%";MySQL> SELECT * FROM pet WHERE name REGEXP "^b";
    • MySQL> SELECT species, COUNT(*) FROM pet GROUP BY species;MySQL> SELECT MAX(article) AS article FROM shop;MySQL> SELECT * FROM employee WHERE name LIKE "%Sm%";MySQL> SELECT * FROM employee WHERE name REGEXP "^Ja";Insert:MySQL> INSERT INTO employee VALUES ("Jane Smith","Sales","Custome Rep");MySQL> INSERT INTO employee VALUES (Jane Smith,Sales,Account Manager);MySQL> INSERT INTO employee VALUES (Jane smith’,’Engineein’,’Manager’);MySQL> UPDATE employee SET dept=HR WHERE name=Jane Smith; Insert data into a table and its columns within a specific database:mysql> INSERT INTO mytable VALUES(column1data,column2data,column3data,column4data,column5data,column6data,column7data,column8data,column9data); Update data in a specific table, column, field:Mysql> UPDATE mytable SET column1="mydata" WHERE column2="mydata";