Archive for the ‘MySQL Querying’ Category

Basic MySQL Commands

Posted: March 8, 2011 in MySQL Querying

I found a good source of pretty much all MySQL commands. It could be useful when you are busy programming with php and you get stuck trying to communicate with the DataBase.

A heads up to you in advance, I am as of now working on consolidation some of the PHP programming issues that you might encounter while you busy programming. I would be bringing out the issues as well as the solutions/workarounds for the same. Hopefully that should be done within a day or two. Till then continue going through the list of commands below.

To login (from unix shell) use -h only if needed.

# [mysql dir]/bin/mysql -h hostname -u root -p

Create a database on the sql server.

mysql> create database [databasename];

List all databases on the sql server.

mysql> show databases;

Switch to a database.

mysql> use [db name];

To see all the tables in the db.

mysql> show tables;

To see database’s field formats.

mysql> describe [table name];

To delete a db.

mysql> drop database [database name];

To delete a table.

mysql> drop table [table name];

Show all data in a table.

mysql> SELECT * FROM [table name];

Returns the columns and column information pertaining to the designated table.

mysql> show columns from [table name];

Show certain selected rows with the value “whatever”.

mysql> SELECT * FROM [table name] WHERE [field name] = “whatever”;

Show all records containing the name “Bob” AND the phone number ‘3444444’.

mysql> SELECT * FROM [table name] WHERE name = “Bob” AND phone_number = ‘3444444’;

Show all records not containing the name “Bob” AND the phone number ‘3444444’ order by the phone_number field.

mysql> SELECT * FROM [table name] WHERE name != “Bob” AND phone_number = ‘3444444’ order by phone_number;

Show all records starting with the letters ‘bob’ AND the phone number ‘3444444’.

mysql> SELECT * FROM [table name] WHERE name like “Bob%” AND phone_number = ‘3444444’;

Show all records starting with the letters ‘bob’ AND the phone number ‘3444444’ limit to records 1 through 5.

mysql> SELECT * FROM [table name] WHERE name like “Bob%” AND phone_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.

mysql> SELECT * FROM [table name] WHERE rec RLIKE “^a”;

Show unique records.

mysql> SELECT DISTINCT [column name] FROM [table name];

Show selected records sorted in an ascending (asc) or descending (desc).

mysql> SELECT [col1],[col2] FROM [table name] ORDER BY [col2] DESC;

Return number of rows.

mysql> SELECT COUNT(*) FROM [table name];

Sum column.

mysql> SELECT SUM(*) FROM [table name];

Join tables on common columns.

mysql> select lookup.illustrationid, lookup.personid,person.birthday from lookup left join person on lookup.personid=person.personid=statement to join birthday in person table with primary illustration id;

Creating a new user. Login as root. Switch to the MySQL db. Make the user. Update privs.

# mysql -u root -p
mysql> use mysql;
mysql> INSERT INTO user (Host,User,Password) VALUES(‘%’,’username’,PASSWORD(‘password’));
mysql> flush privileges;

Change a users password from unix shell.

# [mysql dir]/bin/mysqladmin -u username -h hostname.blah.org -p password ‘new-password’

Change a users password from MySQL prompt. Login as root. Set the password. Update privs.

# mysql -u root -p
mysql> SET PASSWORD FOR ‘user’@’hostname’ = PASSWORD(‘passwordhere’);
mysql> flush privileges;

Recover a MySQL root password. Stop the MySQL server process. Start again with no grant tables. Login to MySQL as root. Set new password. Exit MySQL and restart MySQL server.

# /etc/init.d/mysql stop
# mysqld_safe –skip-grant-tables &
# mysql -u root
mysql> use mysql;
mysql> update user set password=PASSWORD(“newrootpassword”) where User=’root’;
mysql> flush privileges;
mysql> quit
# /etc/init.d/mysql stop
# /etc/init.d/mysql start

Set a root password if there is on root password.

# mysqladmin -u root password newpassword

Update a root password.

# mysqladmin -u root -p oldpassword newpassword

Allow the user “bob” to connect to the server from localhost using the password “passwd”. Login as root. Switch to the MySQL db. Give privs. Update privs.

# mysql -u root -p
mysql> use mysql;
mysql> grant usage on *.* to bob@localhost identified by ‘passwd’;
mysql> flush privileges;

Give user privilages for a db. Login as root. Switch to the MySQL db. Grant privs. Update privs.

# mysql -u root -p
mysql> use mysql;
mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,Create_priv,Drop_priv) VALUES (‘%’,’databasename’,’username’,’Y’,’Y’,’Y’,’Y’,’Y’,’N’);
mysql> flush privileges;

or

mysql> grant all privileges on databasename.* to username@localhost;
mysql> flush privileges;

To update info already in a table.

mysql> UPDATE [table name] SET Select_priv = ‘Y’,Insert_priv = ‘Y’,Update_priv = ‘Y’ where [field name] = ‘user’;

Delete a row(s) from a table.

mysql> DELETE from [table name] where [field name] = ‘whatever’;

Update database permissions/privilages.

mysql> flush privileges;

Delete a column.

mysql> alter table [table name] drop column [column name];

Add a new column to db.

mysql> alter table [table name] add column [new column name] varchar (20);

Change column name.

mysql> alter table [table name] change [old column name] [new column name] varchar (50);

Make a unique column so you get no dupes.

mysql> alter table [table name] add unique ([column name]);

Make a column bigger.

mysql> alter table [table name] modify [column name] VARCHAR(3);

Delete unique from table.

mysql> alter table [table name] drop index [colmn name];

Load a CSV file into a table.

mysql> LOAD DATA INFILE ‘/tmp/filename.csv’ replace INTO TABLE [table name] FIELDS TERMINATED BY ‘,’ LINES TERMINATED BY ‘\n’ (field1,field2,field3);

Dump all databases for backup. Backup file is sql commands to recreate all db’s.

# [mysql dir]/bin/mysqldump -u root -ppassword –opt >/tmp/alldatabases.sql

Dump one database for backup.

# [mysql dir]/bin/mysqldump -u username -ppassword –databases databasename >/tmp/databasename.sql

Dump a table from a database.

# [mysql dir]/bin/mysqldump -c -u username -ppassword databasename tablename > /tmp/databasename.tablename.sql

Restore database (or database table) from backup.

# [mysql dir]/bin/mysql -u username -ppassword databasename < /tmp/databasename.sql

Create Table Example 1.

mysql> CREATE TABLE [table name] (firstname VARCHAR(20), middleinitial VARCHAR(3), lastname VARCHAR(35),suffix VARCHAR(3),officeid VARCHAR(10),userid VARCHAR(15),username VARCHAR(8),email VARCHAR(35),phone VARCHAR(25), groups VARCHAR(15),datestamp DATE,timestamp time,pgpemail VARCHAR(255));

Create Table Example 2.

mysql> create table [table name] (personid int(50) not null auto_increment primary key,firstname varchar(35),middlename varchar(50),lastnamevarchar(50) default ‘bato’);

Thanks for your interest in this site. I will try to bring in more and more interesting posts. Till then happy and adventurous programming.

Advertisements

1st of all I’ll start with the creation of database

I will begin with the step to  start/open the MySQL Terminal/Prompt (Drop your comment below regarding the right usage of the terminology) because this is where most of the beginners end up with. I myself did get into this trouble wondering where to begin with.

Open your Terminal window of your Ubuntu desktop. Basic workflow for other Linux Desktops could also be the same except with slight variations.

You can do this by:
Click on Applications -> Accessories -> Terminal.

At the prompt type the following:
revindran@revindran-desktop:~$ mysql -u root -p

The ‘root’ in the above command should be replaced by the name if you have specified one at the time of installation. If you haven’t, then your root username is ‘root’.

You would be prompted to type the password of your MySql root.

Enter the password. Don’t worry if the asterisk(*) characters do not appear on your screen. It is hidden for added security.
Just type in the password and press ‘Return’ (‘Enter’) key of your keyboard.

Then comes your mysql prompt.
The following screenshot must give you a brief summary all you have done till now.

Starting MYSQL Terminal

Starting MYSQL Terminal

Congrats. You can now get started with your SQL querying now.

To create the Database.
Enter the following at the mysql prompt.

mysql> CREATE DATABASE trialDB;

It should output the following lines. Ignore the seconds:
Query OK, 1 row affected (0.00 sec)

So you are done with creation of a Database named trialDB.

Now to create the table in the Database that you just created.

Type ‘exit’ at mysql prompt without the quotes which should look something like this as shown below:

mysql> exit;
Bye

Now you are back to your terminal.
Now type the following in your terminal and press enter.

log into MySQL Database

log into MySQL Database that was just created

However note that I did read at certain sources that we could directly select the database by typing with following syntax without having to log out of the mysql prompt by typing exit.

mysql>use trialDB;

However this was throwing an error when I tried executing it. Sorry it is not possible for me to execute it again as I don’t have access to MySQL right now.
However if somebody could come out with an explanation, then please drop in your experience below in the comment box.

Ok. Let continue.

Now that you have selected the database, we will now create a table.

mysql> CREATE TABLE `trialTBLE` ( `member_id` int(11) unsigned NOT NULL,`member_name` varchar(200) NOT NULL) TYPE=InnoDB;

To learn more about the above query’s usage and syntax, follow this link:
Very good SQL Tutorial

Following must be the output of the above command executed. Ignore the seconds.
Query OK, 0 rows affected, 1 warning (0.08 sec)

Bingo so you are done. In the upcoming days, I will be posting on how to run these commands using PHP which would be quite interesting.

Also I would be posting a Utility post of SQL Querying which can come in handy to understand the structure of the Databases, tables and data that you maintain in the MySQL Database.

Till then have a blast. Don’t forget to drop in your doubts or easier methods if any in the comment box below so that it could be of help to somebody in need and I could learn from it as well.