Mbbt. Sql tili

[index_name] (col_name, ...)

REFERENCES tbl_name (col_name,...)

[ON DELETE reference_option]

[ON UPDATE reference_option]

reference_option:

RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT

FOREIGN KEY yaratish

CREATE TABLE Orders (

OrderID int NOT NULL,

OrderNumber int NOT NULL,

PersonID int,

PRIMARY KEY (OrderID),

CONSTRAINT FK_PersonOrder

FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)

);

ALTER TABLE Orders

ADD CONSTRAINT FK_PersonOrder

FOREIGN KEY (PersonID)

REFERENCES Persons(PersonID);

ALTER TABLE Orders DROP FOREIGN KEY FK_PersonOrder;

MySql. WHERE

SELECT select_list

FROM table_name

WHERE search_condition;

search_condition: mantiqiy ifodalar, AND, OR, NOT

WHERE

SELECT lastname, firstname, jobtitle

FROM employees

WHERE jobtitle = 'Sales Rep';

WHERE

SELECT lastname, firstname, jobtitle, officeCode

FROM employees

WHERE jobtitle = 'Sales Rep' AND officeCode = 1;

ORDER BY

SELECT lastName, firstName, jobTitle, officeCode

FROM employees

WHERE

jobtitle = 'Sales Rep' OR officeCode = 1

ORDER BY

officeCode , jobTitle;