Mysql

Basic examples

Some examples: (to be completed)

show Tables;

% is anything

select UserName, Password from Users where UserName like "Pi%"

select * from Users;

delete from ---- where ----=1;

if autocommit=false it is needed to do after any modification/delete:

commit;

List all tables and show their sizes in MB (useful to troubleshoot prestashop):

SELECT TABLE_SCHEMA AS `Database`,   TABLE_NAME AS `Table`,   ROUND((DATA_LENGTH + INDEX_LENGTH) / 1024 / 1024) AS `Size (MB)` FROM   information_schema.TABLES ORDER BY   (DATA_LENGTH + INDEX_LENGTH) DESC;

Clean Prestashop DB:

use prestashopdafyn;
TRUNCATE TABLE psdafyn_connections;
TRUNCATE TABLE psdafyn_connections_source;
TRUNCATE TABLE psdafyn_connections_page;
TRUNCATE TABLE psdafyn_pagenotfound;
TRUNCATE TABLE ps_statssearch;
#  despres cal anar a modul database optimisation https://filateliatrafalgar.com/admin2/index.php?controller=AdminModules&token=24c4d2cab9cd70a42db26d7c70bd8808&configure=dboptimization&tab_module=administration&module_name=dboptimization  i clicar a clean de "unwanted carts" i "guests"

# https://prestacraft.com/clearing-unnecessary-data-from-prestashop-database/#
# Some people recommend to clear also ps_guest table but I would not do that. Why? Because guests infos are located in more tables, so those informations (based on guests IDs) would not have connection to specific guests (when you would clear main guest table).
# --> millor fer-ho amb el modul

Crear base de dades MySQL (Actualitzat: Ja no cal, es pot fer posant root account a la web de configuracio):

mysql -u root -p mysql

I aleshores executar les següents commandes mysql:

create database wikidb;

grant all on wikidb.* to 'wikiuser'@'localhost' identified by 'yourpassword';

o més especific:

grant create, select, insert, update, delete, alter, lock tables on wikidb.* to 'wikiuser'@'localhost';
set password for 'wikiuser'@'localhost'=password('yourpassword');

flush privileges;
\q

create database wikidb; grant create, select, insert, update, delete, alter, lock tables on wikidb.* to 'wikiuser'@'localhost' identified by 'password'; flush privileges; set password for 'wikiuser'@'localhost'=password('yourpassword'); \q

Basics

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');

Més info: http://www.pantz.org/software/mysql/mysqlcommands.html

Repair

Info from: https://www.vps.net/community/knowledgebase/display/SA/How+To+Repair+A+MySQL+Database

Although, Mysqlcheck and Myisamchk are similar in purpose, there are some essential differences. Mysqlcheck as well as Myisamchk can check, repair and analyze MyISAM tables. Mysqlcheck can also check InnoDB tables.

Log in as ‘root’ via SSH and:

Shows you if any need repair:

myisamchk --check /var/lib/mysql/*/*.MYI

Then try ‘safe-recover’ first:

myisamchk --safe-recover /var/lib/mysql/*/*.MYI

and, if neither that nor this works:

myisamchk --recover /var/lib/mysql/*/*.MYI

Then use the ‘force’ flag:

myisamchk --recover --extend-check --force /var/lib/mysql/*/*.MYI

If those are not MyISAM tables try Mysqlcheck:

mysqlcheck --all-databases -p -r #repair databases
mysqlcheck --all-databases -p -a #analyze databases
mysqlcheck --all-databases -p -o #optimize databases

to repair one database:

mysqlcheck -ro database_name

to repair one table in database:

mysqlcheck -ro database_name table_name