create table price_table ( item_id int, price_date date , price int ); delete from price_table; insert into price_table values (1,'2023-01-02',10) ,(1,'2023-02-03',100) ,(1,'2023-02-15',15) ,(1,'2023-03-03',18) ,(1,'2023-03-02',150) ,(2,'2023-03-20',150) ,(2,'2023-03-27',150) ,(3,'2023-03-28',120) ,(3,'2023-04-06',280) ,(4,'2023-03-27',150); -- ,(2,'2023-04-06',20);; select * from price_table order by price_date; with cte as ( SELECT *, month(price_date) as mnth, date_format(concat(year(price_date), '-', month(price_date), '-01'), '%Y-%m-%d') AS first_day_of_month, lag(price,1,"NA") over(partition by item_id order by price_date) as prev_value, count(*) over(partition by item_id,month(price_date) order by price_date) as cnt FROM (select * from price_table order by price_date ) y ) SELECT item_id,first_day_of_month, price_on_first_date FROM ( select * , case when price_date> first_day_of_month AND CNT = 1 then prev_value when price_date = first_day_of_month AND CNT = 1 then price ELSE NULL END AS price_on_first_date from cte ) x WHERE price_on_first_date IS NOT NULL ; -- slightly different approch with cte as ( select * from ( select * , row_number() over(partition by item_id, month(price_date) order by price_date desc) as rn from ( select *, date_format(concat(year(price_date), "-", month(price_date), "-", 01), "%Y-%m-%d") as start_dt -- date_format(price_date, "%v") as day_week_number from price_table order by price_date ) x ) y where rn=1 ) select item_id, start_dt, price_at_start from ( select *, case when price_date > start_dt then prev_price when price_date = start_dt then price end as price_at_start from ( select *, lag(price) over(partition by item_id order by price_date ) as prev_price from cte ) x ) y -- group by 1,2,3
Write, Run & Share MySQL queries online using OneCompiler's MySQL online editor and compiler for free. It's one of the robust, feature-rich online editor and compiler for MySQL. Getting started with the OneCompiler's MySQL editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'MySQL' and start writing queries to learn and test online without worrying about tedious process of installation.
MySQL is a open-source, free and very popular relational database management system which is developed, distributed and supported by Oracle corporation.
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;