For my MySQL query,
update Products
set new_price = (
case when change_date>'2019-08-16' then new_price=100 else new_price end
)
;
the update statement sets the new price to 0. why?
table details:
insert into Products (product_id, new_price, change_date) values ('1', '20', '2019-08-14');
insert into Products (product_id, new_price, change_date) values ('2', '50', '2019-08-14');
insert into Products (product_id, new_price, change_date) values ('1', '30', '2019-08-15');
insert into Products (product_id, new_price, change_date) values ('1', '35', '2019-08-16');
insert into Products (product_id, new_price, change_date) values ('2', '65', '2019-08-17');
insert into Products (product_id, new_price, change_date) values ('3', '20', '2019-08-18');
select * from Products;
You are attempting to set new_price to the result of the boolean expression new_price=100, which will be 0 unless new_price already has the value 100. Just remove the new_price= and the code will work fine:
update Products
set new_price = case when change_date>'2019-08-16' then 100
else new_price
end
Demo on dbfiddle
It sets the value to zero because new_price = 100 is a boolean expression -- and that evaluates to either 0 or 1.
If this is all you are doing, you should filter in the where clause:
update Products
set new_price = 100
where change_date > '2019-08-16';
Related
I am creating a MySQL table with the following query.
CREATE TABLE log_table (id INTEGER, street TEXT, status INTEGER)
and filling it with the following query:
INSERT INTO log_table (`id`, `street`, `status`) VALUES
('1', 'main_street', '0'),
('2', '1st_street', '0'),
('3', '1st_street', '0'),
('4', 'main_street', '0'),
('5', '2nd_street', '0'),
('6', '1st_street', '0'),
('7', 'main_street', '0'),
('8', '2nd_street', '0');
I am trying to update the status column with the count of the street column.
For example for the first row status column should be 3 because main_street appears 3 times in street column.
I have tried the following query but it doesn't work.
UPDATE log_table l1 SET status =
(SELECT COUNT(*) FROM log_table l2 WHERE l2.street = l1.street);
It gives an error that says "You can't specify target table 'l1' for update in FROM clause". What could be the issue?
You can use a join:
UPDATE log_table l1
join (SELECT COUNT(*) as n, street FROM log_table l2 group by l2.street) as l3 on l1.street=l3.street
SET status = l3.n
SQLFiddle
Write a SQL query to find number position as well number and consective number count
CREATE TABLE Logs (
`Id` INTEGER,
`Num` INTEGER
);
INSERT INTO Logs
(`Id`, `Num`)
VALUES
('1', '1'),
('2', '1'),
('3', '1'),
('4', '2'),
('5', '1'),
('6', '2'),
('7', '2');
Prefere Return
StartId Num Count
1 1 3
4 2 1
5 1 1
6 2 2
and also can i get any suggestion which function can be use with case function in MySQL Function
Looking at your data and expected results, I believe your expectations are inconsistent, eg you can either have 1 and 6 or 3 and 7.
What you need to do is group the data by successive num values and aggregate the results.
with gp as (
select *,
Row_Number() over(order by id)
- Row_Number() over(partition by num order by id) g
from logs
)
select Min(id) Id,
num, Count(*) Count
from gp
group by g, num
order by id
I have a table name order_history where I store both old_status and new_status of company orders.
the schema of table :
CREATE TABLE order_history (
id int(11) NOT NULL AUTO_INCREMENT,
old_status longtext COLLATE utf8_unicode_ci,
new_status longtext COLLATE utf8_unicode_ci,
created_at datetime NOT NULL,
order_id int(11) DEFAULT NULL,
PRIMARY KEY (id)
}
The insert to populate is :
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (1, '56', '714', '2020-12-20 21:37:54', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (2, '714', '61', '2020-12-20 21:37:56', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (3, '61', '713', '2020-12-20 21:38:17', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (4, '713', '42', '2020-12-20 21:38:26', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (5, '42', '51', '2020-12-20 21:59:17', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (6, '56', '714', '2020-12-20 22:21:27', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (7, '714', '61', '2020-12-20 22:21:29', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (8, '61', '713', '2020-12-20 22:24:28', 94471496);
INSERT INTO order_history (id, old_status, new_status, created_at, order_id) VALUES (9, '713', '42', '2020-12-20 22:24:43', 94471496);
And Now the question I want to find the TIMEDIFF of created_ats between rows that new_status=61 and rows that new_status=42 and old_status=713.
So in the example the affected rows should be (2,4,7,9) , and the right answer will be the TIMEDIFF between rows with ids (2,4) and rows with ids (7,9). But my query returns 3 results instead of 2 and it also calculate the TIMEDIFF between rows (2,9).
How can I exclude this result?
Here is my query:
select *
from (select oschStart.order_id as order_id, TIMEDIFF(oschEnd.created_at, oschStart.created_at) as confirm_time
from (select osch1.order_id, osch1.created_at
from order_history osch1
where osch1.old_status = 713
and osch1.new_status = 42
) oschEnd
join (select osch1.order_id, osch1.created_at
from order_history osch1
where osch1.new_status = 61
) oschStart
on oschStart.order_id = oschEnd.order_id and oschEnd.created_at > oschStart.created_at) order_time;
A simpler approach is to use a correlated sub query
select *,
timediff(
(select created_at from order_history oh1
where oh1.order_id = oh.order_id and
oh1.id > oh.id and
oh1.old_status = '713' and oh1.new_status = '42'
order by oh1.id asc limit 1),oh.created_at) diff
from order_history oh
where new_status = 61;
Why you have the unwanted results?
oschStart will result rows[2,7] and oschEnd will result rows [4,9]. Joining these subqueries will result in 4 rows [(2,4),(2,9),(7,4),(7,9)]. Your condition (on oschStart.order_id = oschEnd.order_id and oschEnd.created_at > oschStart.created_at) will result in these three rows: [(2,4),(2,9),(7,9)]. It wont prune (2,9) because also 9[created_date] > 2[created_date]. So your query will match a oschStart with all oschEnds that occurs after it. But You need it to be matched with the first occurring oschEnd
Solution
Use group by. If you group by your query results on a field and put other fields on your select part, Mysql will fill those fields with first row of that "group". So assuming that order_history is sorted on created_date you may use this query:
select order_time.id , order_time.*
from (
select oschStart.id as id, oschStart.order_id as order_id,
TIMEDIFF(oschEnd.created_at, oschStart.created_at) as confirm_time
from (select osch1.order_id, osch1.created_at
from order_history osch1
where osch1.old_status = 713
and osch1.new_status = 42
) oschEnd
join (select osch1.id as id, osch1.order_id, osch1.created_at
from order_history osch1
where osch1.new_status = 61
) oschStart
on oschStart.order_id = oschEnd.order_id
and oschEnd.created_at > oschStart.created_at)
order_time
group by order_time.id;
I am trying to insert into a table only if the qty has changed down in another table see example
INSERT INTO sales_items (sale_id, item_id, quantity_purchased, item_cost_price, item_unit_price)
VALUES ('1', '1546', '3', '10', '10')
WHEN (SELECT quantity FROM location_items WHERE location_id =4 AND item_id =1546) < 10;
You can do the following:
INSERT INTO sales_items
(sale_id, item_id, quantity_purchased, item_cost_price, item_unit_price)
VALUES
(SELECT '1', '1546', '3', '10', '10'
FROM location_items
WHERE location_id = 4
AND item_id = 1546
AND quantity < 10
);
Or, if you want to do it all in one query, including updates:
REPLACE INTO sales_items
(item_id, quantity_purchased, item_cost_price, item_unit_price)
VALUES
(SELECT item_id, ??, ??, ??
FROM location_items
WHERE quantity < 10
AND quantity > 0
);
...where you have to fill the ?? with references to columns holding the values for item_cost_price and item_unit_price, and you have a unique constraint on item_id
Not possible like that. An INSERT query cannot have a where clause, period.
You can, hover, do an insert select from:
INSERT INTO ...
SELECT ... FROM ... WHERE (...) < 10
If the SELECT finds no rows, then nothing gets inserted.
I have a table named test_plan (id, unit, num)
I inserted some values
INSERT INTO `test_plan` (`id`, `unit`, `num`) VALUES
('1', '1', '12'),
('2', '1', '13'),
('3', '1', '14'),
('4', '1', '10'),
('5', '2', '10'),
('6', '2', '9'),
('7', '2', '-1'),
('8', '2', '-1'),
('9', '2', '-1'),
('10', '3', '-1'),
('11', '3', '-1'),
('12', '3', '-1');
I have to fetch unit what is fraction of each unit to total unit when num is not equals to -1
i.e.after run the query it display as unit 1 is 100% completed, unit 2 is 40% completed, unit 3 is 0% completed as row wise. I can count the number of each unit but not the how much it completed.
I tried JOIN for this
SELECT a.unit, numb / count(*) as frac FROM test_plan as a
LEFT OUTER JOIN (SELECT unit, count(num) as numb FROM test_plan where num != -1 group by unit) as b
ON a.unit = b.unit group by a.unit;
try this:
select unit,
(sum(case when num = -1 then 0 else 1 end) / count(*)) * 100 as pct_complete
from lecture_plan group by unit;
there's no need for a nested sub query, the combination of aggregation and the case statement is sufficient