CREATE TABLE Reviews ( review_id INT PRIMARY KEY AUTO_INCREMENT, customer_id INT NOT NULL, restaurant_id INT NOT NULL, order_date DATE NOT NULL, rating INT CHECK (rating BETWEEN 1 AND 5), comment TEXT, CONSTRAINT unique_review UNIQUE (customer_id, restaurant_id, order_date, review_id) ); INSERT INTO Reviews (customer_id, restaurant_id, order_date, rating, comment) VALUES -- January Reviews (1, 1, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 5, 'Amazing food!'), (2, 1, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 4, 'Great service.'), (3, 2, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 3, 'Good but overpriced.'), (4, 2, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 5, 'Excellent ambiance.'), (5, 3, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 4, 'Loved the seafood.'), (6, 3, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 3, 'Average taste.'), (7, 1, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 5, 'Perfect meal!'), (8, 2, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 4, 'Nice atmosphere.'), -- February Reviews (1, 1, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 5, 'Delicious!'), (2, 1, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 4, 'Good service.'), (3, 2, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 3, 'A bit salty.'), (4, 2, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 5, 'Great experience.'), (5, 3, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 4, 'Tasty food.'), (6, 3, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 3, 'Could be better.'), (7, 1, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 4, 'Friendly staff.'), (8, 2, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 5, 'Highly recommend!'), -- March Reviews (1, 1, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 5, 'Fantastic!'), (2, 1, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 4, 'Quick service.'), (3, 2, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 3, 'Mediocre taste.'), (4, 2, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 5, 'Best meal ever!'), (5, 3, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 4, 'Authentic flavors.'), (6, 3, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 3, 'Not bad.'), (7, 1, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 5, 'Loved everything!'), (8, 2, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 4, 'Good but pricey.'), -- Duplicate Records (Same customer, restaurant, and order_date) (1, 1, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 5, 'Amazing food!'), -- Duplicate of (1,1) (2, 1, DATE_SUB(CURDATE(), INTERVAL 1 MONTH), 4, 'Great service.'), -- Duplicate of (2,1) (3, 2, DATE_SUB(CURDATE(), INTERVAL 2 MONTH), 3, 'A bit salty.'), -- Duplicate of (3,2) (4, 2, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 5, 'Best meal ever!'), -- Duplicate of (4,2) (5, 3, DATE_SUB(CURDATE(), INTERVAL 3 MONTH), 4, 'Authentic flavors.'); -- Duplicate of (5,3)
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CREATE TABLE table_name (
column1 datatype,
column2 datatype,
....);
CREATE TABLE EMPLOYEE (
empId INTEGER PRIMARY KEY,
name TEXT NOT NULL,
dept TEXT NOT NULL
);
ALTER TABLE Table_name ADD column_name datatype;
INSERT INTO EMPLOYEE VALUES (0001, 'Dave', 'Sales');
TRUNCATE table table_name;
DROP TABLE table_name;
RENAME TABLE table_name1 to new_table_name1;
--Line1;
/* Line1,
Line2 */
INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);
Note: Column names are optional.
INSERT INTO EMPLOYEE VALUES (0001, 'Ava', 'Sales');
SELECT column1, column2, ...
FROM table_name
[where condition];
SELECT * FROM EMPLOYEE where dept ='sales';
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
UPDATE EMPLOYEE SET dept = 'Sales' WHERE empId='0001';
DELETE FROM table_name where condition;
DELETE from EMPLOYEE where empId='0001';
CREATE INDEX index_name on table_name(column_name);
CREATE UNIQUE INDEX index_name on table_name(column_name);
DROP INDEX index_name ON table_name;
Creating a View:
CREATE VIEW View_name AS
Query;
SELECT * FROM View_name;
ALTER View View_name AS
Query;
DROP VIEW View_name;
CREATE TRIGGER trigger_name trigger_time trigger_event
ON tbl_name FOR EACH ROW [trigger_order] trigger_body
/* where
trigger_time: { BEFORE | AFTER }
trigger_event: { INSERT | UPDATE | DELETE }
trigger_order: { FOLLOWS | PRECEDES } */
DROP TRIGGER [IF EXISTS] trigger_name;
CREATE PROCEDURE sp_name(p1 datatype)
BEGIN
/*Stored procedure code*/
END;
CALL sp_name;
DROP PROCEDURE sp_name;
SELECT * FROM TABLE1 INNER JOIN TABLE2 where condition;
SELECT * FROM TABLE1 LEFT JOIN TABLE2 ON condition;
SELECT * FROM TABLE1 RIGHT JOIN TABLE2 ON condition;
SELECT select_list from TABLE1 CROSS JOIN TABLE2;