Mysql note

from w3cschool.com

1,modify the segment of table

alter table table_name add/drop var_name [var_type];

2,update

UPDATE table_name SET field1=new-value1, field2=new-value2
[WHERE Clause]

3,like==regexp

SELECT field1, field2,...fieldN table_name1, table_name2...
WHERE field1 LIKE condition1 [AND [OR]] filed2 = 'somevalue'

4,drop

DROP TABLE table_name ;

drop db_name;

5,create

mysql> CREATE TABLE tutorials_tbl(
   -> tutorial_id INT NOT NULL AUTO_INCREMENT,
   -> tutorial_title VARCHAR(100) NOT NULL,
   -> tutorial_author VARCHAR(40) NOT NULL,
   -> submission_date DATE,
   -> PRIMARY KEY ( tutorial_id )
   -> );

create db_name

6,delete

DELETE FROM table_name [WHERE Clause]

7,order by

SELECT field1, field2,...fieldN table_name1, table_name2...
ORDER BY field1, [field2...] [ASC [DESC]]

8,INDEX

9,temp table

mysql> CREATE TEMPORARY TABLE SalesSummary (
    -> product_name VARCHAR(50) NOT NULL
    -> , total_sales DECIMAL(12,2) NOT NULL DEFAULT 0.00
    -> , avg_unit_price DECIMAL(7,2) NOT NULL DEFAULT 0.00
    -> , total_units_sold INT UNSIGNED NOT NULL DEFAULT 0
);

10,create clone table

mysql> SHOW CREATE TABLE tutorials_tbl \G;

mysql> CREATE TABLE `clone_tbl` (...);

mysql> INSERT INTO clone_tbl (tutorial_id,
    ->                        tutorial_title,
    ->                        tutorial_author,
    ->                        submission_date)
    -> SELECT tutorial_id,tutorial_title,
    ->        tutorial_author,submission_date,
    -> FROM tutorials_tbl;

11,mysql info

SELECT VERSION( )   
SELECT DATABASE( )   current dbname
SELECT USER( )    current user
SHOW STATUS   
SHOW VARIABLES

12,AUTO_INCREMENT

reset table

insert table with id acsend

mysql> CREATE TABLE insect
    -> (
    -> id INT UNSIGNED NOT NULL AUTO_INCREMENT = 100,
    -> PRIMARY KEY (id),
    -> name VARCHAR(30) NOT NULL, # type of insect
    -> date DATE NOT NULL, # date collected
    -> origin VARCHAR(30) NOT NULL # where collected
);

13,primary key,unique // The UNIQUE constraint uniquely identifies each record in a database table.

CREATE TABLE person_tbl
(
   first_name CHAR(20) NOT NULL,
   last_name CHAR(20) NOT NULL,
   sex CHAR(10),
   PRIMARY KEY (last_name, first_name)  //last_name not permit to be the same as  first_name
);

CREATE TABLE person_tbl
(
   first_name CHAR(20) NOT NULL,
   last_name CHAR(20) NOT NULL,
   sex CHAR(10)
   UNIQUE (last_name, first_name)  // INSERT IGNORE INTO person_tbl (last_name, first_name),insert record existed will not report err,either real insert it
);

14,export &LOAD

SELECT a,b,a+b INTO OUTFILE '/tmp/result.text'

FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
LINES TERMINATED BY '\n'
FROM test_table;

---

mysql> LOAD DATA LOCAL INFILE 'dump.txt' INTO TABLE mytbl
-> FIELDS TERMINATED BY ':'
-> LINES TERMINATED BY '\r\n';

mysql> LOAD DATA LOCAL INFILE 'dump.txt'
-> INTO TABLE mytbl (b, c, a); //specialize the order

---

mysqlimport dbname tablename.txt

15,Function

SELECT AVG(Price) AS PriceAverage FROM Products;

SELECT COUNT(*) AS NumberOfOrders FROM Orders;

SELECT FIRST(column_name) FROM table_name;

SELECT LAST(column_name) FROM table_name;

SELECT MAX(column_name) FROM table_name;

SELECT MIN(column_name) FROM table_name;

SELECT SUM(column_name) FROM table_name;

SELECT Shippers.ShipperName,COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders
LEFT JOIN Shippers
ON Orders.ShipperID=Shippers.ShipperID
GROUP BY ShipperName;

SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders FROM (Orders
INNER JOIN Employees
ON Orders.EmployeeID=Employees.EmployeeID)
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 10;

SELECT UCASE(CustomerName) AS Customer, City
FROM Customers;

SELECT LCASE(CustomerName) AS Customer, City   //extract characters from a text field
FROM Customers;

SELECT LEN(column_name) FROM table_name;

select round(2.555,2) from dual;

SELECT NOW() FROM dual;

SELECT ProductName, Price, FORMAT(Now(),'YYYY-MM-DD') AS PerDate
FROM Products;

FOREIGN KEY constraint is used to prevent actions that would destroy links between tables

CREATE TABLE Orders
(
O_Id int NOT NULL,
OrderNo int NOT NULL,
P_Id int,
PRIMARY KEY (O_Id),
FOREIGN KEY (P_Id) REFERENCES Persons(P_Id)
)

to be added...