MySQL Database
MySQL Notes
MySQL
Getting started:
Related tutorials:
- MySQL-CLI: https://www.youtube.com/playlist?list=PLfdtiltiRHWEw4-kRrh1ZZy_3OcQxTn7P
- Analyzing Business Metrics: https://www.codecademy.com/learn/sql-analyzing-business-metrics
- SQL joins infografic: http://cd64.de/sql-joins
Tools:
- DataGrip: https://www.jetbrains.com/datagrip/
- Sequel Pro: http://www.sequelpro.com/
Commands
Access monitor: mysql -u [username] -p; (will prompt for password)
Show all databases: show databases;
Access database: mysql -u [username] -p [database] (will prompt for password)
Create new database: create database [database];
Select database: use [database];
Determine what database is in use: select database();
Show all tables: show tables;
Show table structure: describe [table];
List all indexes on a table: show index from [table];
Create new table with columns: CREATE TABLE [table] ([column] VARCHAR(120), [another-column] DATETIME);
Adding a column: ALTER TABLE [table] ADD COLUMN [column] VARCHAR(120);
Adding a column with an unique, auto-incrementing ID: ALTER TABLE [table] ADD COLUMN [column] int NOT NULL AUTO_INCREMENT PRIMARY KEY;
Inserting a record: INSERT INTO [table] ([column], [column]) VALUES ('[value]', [value]');
MySQL function for datetime input: NOW()
Selecting records: SELECT * FROM [table];
Explain records: EXPLAIN SELECT * FROM [table];
Selecting parts of records: SELECT [column], [another-column] FROM [table];
Counting records: SELECT COUNT([column]) FROM [table];
Counting and selecting grouped records: SELECT *, (SELECT COUNT([column]) FROM [table]) AS count FROM [table] GROUP BY [column];
Selecting specific records: SELECT * FROM [table] WHERE [column] = [value]; (Selectors: <, >, !=; combine multiple selectors with AND, OR)
Select records containing [value]: SELECT * FROM [table] WHERE [column] LIKE '%[value]%';
Select records starting with [value]: SELECT * FROM [table] WHERE [column] LIKE '[value]%';
Select records starting with val and ending with ue: SELECT * FROM [table] WHERE [column] LIKE '[val_ue]';
Select a range: SELECT * FROM [table] WHERE [column] BETWEEN [value1] and [value2];
Select with custom order and only limit: SELECT * FROM [table] WHERE [column] ORDER BY [column] ASC LIMIT [value]; (Order: DESC, ASC)
Updating records: UPDATE [table] SET [column] = '[updated-value]' WHERE [column] = [value];
Deleting records: DELETE FROM [table] WHERE [column] = [value];
Delete all records from a table (without dropping the table itself): DELETE FROM [table]; (This also resets the incrementing counter for auto generated columns like an id column.)
Delete all records in a table: truncate table [table];
Removing table columns: ALTER TABLE [table] DROP COLUMN [column];
Deleting tables: DROP TABLE [table];
Deleting databases: DROP DATABASE [database];
Custom column output names: SELECT [column] AS [custom-column] FROM [table];
Export a database dump (more info here): mysqldump -u [username] -p [database] > db_backup.sql
Use --lock-tables=false option for locked tables (more info here).
Import a database dump (more info here): mysql -u [username] -p -h localhost [database] < db_backup.sql
Logout: exit;
Aggregate functions
Select but without duplicates: SELECT distinct name, email, acception FROM owners WHERE acception = 1 AND date >= 2015-01-01 00:00:00
Calculate total number of records: SELECT SUM([column]) FROM [table];
Count total number of [column] and group by [category-column]: SELECT [category-column], SUM([column]) FROM [table] GROUP BY [category-column];
Get largest value in [column]: SELECT MAX([column]) FROM [table];
Get smallest value: SELECT MIN([column]) FROM [table];
Get average value: SELECT AVG([column]) FROM [table];
Get rounded average value and group by [category-column]: SELECT [category-column], ROUND(AVG([column]), 2) FROM [table] GROUP BY [category-column];
Multiple tables
Select from multiple tables: SELECT [table1].[column], [table1].[another-column], [table2].[column] FROM [table1], [table2];
Combine rows from different tables: SELECT * FROM [table1] INNER JOIN [table2] ON [table1].[column] = [table2].[column];
Combine rows from different tables but do not require the join condition: SELECT * FROM [table1] LEFT OUTER JOIN [table2] ON [table1].[column] = [table2].[column]; (The left table is the first table that appears in the statement.)
Rename column or table using an alias: SELECT [table1].[column] AS '[value]', [table2].[column] AS '[value]' FROM [table1], [table2];
Users functions
List all users: SELECT User,Host FROM mysql.user;
Create new user: CREATE USER 'username'@'localhost' IDENTIFIED BY 'password';
Grant ALL access to user for * tables: GRANT ALL ON database.* TO 'user'@'localhost';
Find out the IP Address of the Mysql Host
SHOW VARIABLES WHERE Variable_name = 'hostname'; (source)
Export and Import
For Export:
mysqldump -u [user] -p [db_name] | gzip > [filename_to_compress.sql.gz]
For Import:
gunzip < [compressed_filename.sql.gz] | mysql -u [user] -p[password] [databasename]
Connect/Disconnect
mysql -h <host> -u <user> -p<passwd> mysql -h <host> -u <user> -p Enter password: ******** mysql -u user -p mysql mysql -h <host> -u <user> -p <Database>
Query
SELECT * FROM table
SELECT * FROM table1, table2, ...
SELECT field1, field2, ... FROM table1, table2, ...
SELECT ... FROM ... WHERE condition
SELECT ... FROM ... WHERE condition GROUP BY field
SELECT ... FROM ... WHERE condition GROUP BY field HAVING condition2
SELECT ... FROM ... WHERE condition ORDER BY field1, field2
SELECT ... FROM ... WHERE condition ORDER BY field1, field2 DESC
SELECT ... FROM ... WHERE condition LIMIT 10
SELECT DISTINCT field1 FROM ...
SELECT DISTINCT field1, field2 FROM ...
SELECT ... FROM t1 JOIN t2 ON t1.id1 = t2.id2 WHERE condition
SELECT ... FROM t1 LEFT JOIN t2 ON t1.id1 = t2.id2 WHERE condition
SELECT ... FROM t1 JOIN (t2 JOIN t3 ON ...) ON ...
SELECT ... FROM t1 JOIN t2 USING(id) WHERE condition
Conditionals
field1 = value1
field1 <> value1
field1 LIKE 'value _ %'
field1 IS NULL
field1 IS NOT NULL
field1 IN (value1, value2)
field1 NOT IN (value1, value2)
condition1 AND condition2
condition1 OR condition2
Data Manipulation
INSERT INTO table1 (field1, field2, ...) VALUES (value1, value2, ...)
INSERT table1 SET field1=value_1, field2=value_2 ...
LOAD DATA INFILE '/tmp/mydata.txt' INTO TABLE table1
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' ESCAPED BY '\\'
DELETE FROM table1 / TRUNCATE table1
DELETE FROM table1 WHERE condition
-- join:
DELETE FROM table1, table2 WHERE table1.id1 = table2.id2 AND condition
UPDATE table1 SET field1=new_value1 WHERE condition
-- join:
UPDATE table1, table2 SET field1=new_value1, field2=new_value2, ...
WHERE table1.id1 = table2.id2 AND condition
Browsing
SHOW DATABASES
SHOW TABLES
SHOW FIELDS FROM table / SHOW COLUMNS FROM table / DESCRIBE table / DESC table / EXPLAIN table
SHOW CREATE TABLE table
SHOW CREATE TRIGGER trigger
SHOW TRIGGERS LIKE '%update%'
SHOW PROCESSLIST
KILL process_number
SELECT table_name, table_rows FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = '**yourdbname**';
$ mysqlshow
$ mysqlshow database
Create / delete / select / alter database
CREATE DATABASE [IF NOT EXISTS] mabase [CHARACTER SET charset] [COLLATE collation]
CREATE DATABASE mabase CHARACTER SET utf8
DROP DATABASE mabase
USE mabase
ALTER DATABASE mabase CHARACTER SET utf8
Create/delete/modify table
CREATE TABLE table (field1 type1, field2 type2, ...)
CREATE TABLE table (field1 type1 unsigned not null auto_increment, field2 type2, ...)
CREATE TABLE table (field1 type1, field2 type2, ..., INDEX (field))
CREATE TABLE table (field1 type1, field2 type2, ..., PRIMARY KEY (field1))
CREATE TABLE table (field1 type1, field2 type2, ..., PRIMARY KEY (field1, field2))
CREATE TABLE table1 (fk_field1 type1, field2 type2, ...,
FOREIGN KEY (fk_field1) REFERENCES table2 (t2_fieldA)
[ON UPDATE] [CASCADE|SET NULL|RESTRICT]
[ON DELETE] [CASCADE|SET NULL|RESTRICT])
CREATE TABLE table1 (fk_field1 type1, fk_field2 type2, ...,
FOREIGN KEY (fk_field1, fk_field2) REFERENCES table2 (t2_fieldA, t2_fieldB))
CREATE TABLE table IF NOT EXISTS (...)
CREATE TABLE new_tbl_name LIKE tbl_name
[SELECT ... FROM tbl_name ...]
CREATE TEMPORARY TABLE table (...)
CREATE table new_table_name as SELECT [ *|column1, column2 ] FROM table_name
DROP TABLE table
DROP TABLE IF EXISTS table
DROP TABLE table1, table2, ...
DROP TEMPORARY TABLE table
ALTER TABLE table MODIFY field1 type1
ALTER TABLE table MODIFY field1 type1 NOT NULL ...
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1 NOT NULL ...
ALTER TABLE table ALTER field1 SET DEFAULT ...
ALTER TABLE table ALTER field1 DROP DEFAULT
ALTER TABLE table ADD new_name_field1 type1
ALTER TABLE table ADD new_name_field1 type1 FIRST
ALTER TABLE table ADD new_name_field1 type1 AFTER another_field
ALTER TABLE table DROP field1
ALTER TABLE table ADD INDEX (field);
ALTER TABLE table ADD PRIMARY KEY (field);
-- Change field order:
ALTER TABLE table MODIFY field1 type1 FIRST
ALTER TABLE table MODIFY field1 type1 AFTER another_field
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1 FIRST
ALTER TABLE table CHANGE old_name_field1 new_name_field1 type1 AFTER another_field
ALTER TABLE old_name RENAME new_name;
Keys
CREATE TABLE table (..., PRIMARY KEY (field1, field2))
CREATE TABLE table (..., FOREIGN KEY (field1, field2) REFERENCES table2 (t2_field1, t2_field2))
ALTER TABLE table ADD PRIMARY KEY (field);
ALTER TABLE table ADD CONSTRAINT constraint_name PRIMARY KEY (field, field2);
create/modify/drop view
CREATE VIEW view AS SELECT ... FROM table WHERE ...
Privileges
CREATE USER 'user'@'localhost' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON base.* TO 'user'@'localhost' IDENTIFIED BY 'password';
GRANT SELECT, INSERT, DELETE ON base.* TO 'user'@'localhost' IDENTIFIED BY 'password';
REVOKE ALL PRIVILEGES ON base.* FROM 'user'@'host'; -- one permission only
REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'user'@'host'; -- all permissions
SET PASSWORD = PASSWORD('new_pass')
SET PASSWORD FOR 'user'@'host' = PASSWORD('new_pass')
SET PASSWORD = OLD_PASSWORD('new_pass')
DROP USER 'user'@'host'
Main data types
TINYINT (1o: -127+128) SMALLINT (2o: +-65 000) MEDIUMINT (3o: +-16 000 000) INT (4o: +-2 000 000 000) BIGINT (8o: +-9.10^18) Precise interval: -(2^(8*N-1)) -> (2^8*N)-1 /!\ INT(2) = "2 digits displayed" -- NOT "number with 2 digits max"
INT NOT NULL auto_increment PRIMARY KEY -- auto-counter for PK
FLOAT(M,D) DOUBLE(M,D) FLOAT(D=0->53) /!\ 8,3 -> 12345,678 -- NOT 12345678,123!
TIME (HH:MM) YEAR (AAAA) DATE (AAAA-MM-JJ) DATETIME (AAAA-MM-JJ HH:MM; années 1000->9999) TIMESTAMP (like DATETIME, but 1970->2038, compatible with Unix)
VARCHAR (single-line; explicit size) TEXT (multi-lines; max size=65535) BLOB (binary; max size=65535) Variants for TEXT&BLOB: TINY (max=255) MEDIUM (max=~16000) LONG (max=4Go) Ex: VARCHAR(32), TINYTEXT, LONGBLOB, MEDIUMTEXT
ENUM ('value1', 'value2', ...) -- (default NULL, or '' if NOT NULL)
Forgot root password?
$ /etc/init.d/mysql stop
$ mysqld_safe --skip-grant-tables &
$ mysql # on another terminal
mysql> UPDATE mysql.user SET password=PASSWORD('nouveau') WHERE user='root';
## Kill mysqld_safe from the terminal, using Control + \
$ /etc/init.d/mysql start
Repair tables after unclean shutdown
mysqlcheck --all-databases mysqlcheck --all-databases --fast
Loading data
mysql> SOURCE input_file $ mysql database < filename-20120201.sql $ cat filename-20120201.sql | mysql database
|
|||||||||||||||
|
||||||||||||||||||||||||||||||||||||
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||