MySQL cheatsheet
Meng Ly
Posted on November 1, 2024
1. Browsing
SHOW DATABASES;
SHOW TABLES;
SHOW FIELDS FROM table / DESCRIBE table;
SHOW CREATE TABLE table;
SHOW PROCESSLIST;
KILL process_number;
2. Select
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 ...
3. Select-Join
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 ...
4. Conditions
field1 = value1
field1 <> value1
field1 LIKE 'value _ %'
field1 IS NULL
field1 IS NOT NULL
field1 IS IN (value1, value2)
field1 IS NOT IN (value1, value2)
condition1 AND condition2
condition1 OR condition2
5. Create / Open / Delete Database
CREATE DATABASE DatabaseName;
CREATE DATABASE DatabaseName CHARACTER SET utf8;
USE DatabaseName;
DROP DATABASE DatabaseName;
ALTER DATABASE DatabaseName CHARACTER SET utf8;
6. Backup Database to SQL File
mysqldump -u Username -p dbNameYouWant > databasename_backup.sql
7. Restore from backup SQL File
mysql -u Username -p dbNameYouWant < databasename_backup.sql;
8. Repair Tables After Unclean Shutdown
mysqlcheck --all-databases;
mysqlcheck --all-databases --fast;
9. Insert
INSERT INTO table1 (field1, field2) VALUES (value1, value2);
10. Delete
DELETE FROM table1 / TRUNCATE table1
DELETE FROM table1 WHERE condition
DELETE FROM table1, table2 WHERE table1.id1 =
table2.id2 AND condition
11. Update
UPDATE table1 SET field1=new_value1 WHERE condition;
UPDATE table1, table2 SET field1=new_value1, field2=new_value2, ... WHERE
table1.id1 = table2.id2 AND condition;
12. Create / Delete / Modify Table
12.1 Create
CREATE TABLE table (field1 type1, 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|ON DELETE] [CASCADE|SET NULL]
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 TEMPORARY TABLE table;
12.2 Delete
DROP TABLE table;
DROP TABLE IF EXISTS table;
DROP TABLE table1, table2, ...
12.3 Modify
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);
12.4 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
13. Keys
CREATE TABLE table (..., PRIMARY KEY (field1, field2))
CREATE TABLE table (..., FOREIGN KEY (field1, field2) REFERENCES table2
(t2_field1, t2_field2))
14. Users and Privileges
CREATE USER 'user'@'localhost';
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
FLUSH PRIVILEGES;
SET PASSWORD = PASSWORD('new_pass');
SET PASSWORD FOR 'user'@'host' = PASSWORD('new_pass');
SET PASSWORD = OLD_PASSWORD('new_pass');
DROP USER 'user'@'host';
15. Reset Root Password
$ /etc/init.d/mysql stop
$ mysqld_safe --skip-grant-tables
$ mysql # on another terminal
mysql> UPDATE mysql.user SET password=PASSWORD('new_pass') WHERE user='root';
## Switch back to the mysqld_safe terminal and kill the process using Control + \
$ /etc/init.d/mysql start
💖 💪 🙅 🚩
Meng Ly
Posted on November 1, 2024
Join Our Newsletter. No Spam, Only the good stuff.
Sign up to receive the latest update from our blog.
Related
