CODEWITHSUNDEEP
mysqlsql
vFlav
vFlav

Reputation: 1139

MySQL conditional table update Unknown Column error 1054

I have two tables:

Table_A and Table_B share two columns called ID and CYCLE but Table_B contains multiple occurrences of CYCLE. I want to count the number of occurrences of CYCLE in Table_B and store them in Table_A. For example, if for CYCLE = 42 we have 20 rows that have the same value, I want to count that (i.e. 20) and store it in Table_A under the CYCLE since CYCLE will have the same value (42) but the COUNT column in Table_A for that CYCLE will contain 20. Here is what I have so far:

UPDATE database.Table_A
SET count =
(
SELECT ID, CYCLE,
COUNT(*) FROM database.Table_2
GROUP BY ID, CYCLE
)
WHERE database.Table_1.ID = database.Table_2.ID AND
      database.Table_1.CYCLE = database.Table_2.CYCLE

I keep getting Error Code: 1241. Operand should contain 1 column(s)

Any suggestions for my query?

EDIT 1

The SELECT statement returns two columns. That's what's causing Error Code: 1241 but now that that's solved, I get Error Code: 1054. Unknown column 'database.Table_2.CYCLE' in 'where clause'.

Upvotes: 0

Views: 319

Answers (1)

Drew
Drew

Reputation: 24960

This is an old cut and paste I have for an update with a join and an aggregate:

update based on aggregate against another table

create table tA
(   id int auto_increment primary key,
    theDate datetime not null,
    -- other stuff
    key(theDate) -- make it snappy fast
);

create table tB
(   myId int primary key,   -- but definition PK is not null
    someCol int not null
);

-- truncate table tA;
-- truncate table tB;

insert tA(theDate) values
('2015-09-19'),
('2015-09-19 00:24:21'),
('2015-09-19 07:24:21'),
('2015-09-20 00:00:00');

insert tB(myId,someCol) values (15,-1); --    (-1) just for the heck of it
insert tB(myId,someCol) values (16,-1); --    (-1) just for the heck of it

update tB
set someCol=(select count(*) from tA where theDate between '2015-09-19 00:00:00' and '2015-09-19 00:59:59')
where tB.myId=15;

select * from tB;
+------+---------+
| myId | someCol |
+------+---------+
|   15 |       2 |
|   16 |      -1 |
+------+---------+

only myId=15 is touched.

I will happily delete it if it bothers my peers. In fact I cannot delete it today as I used up all my votes.

Upvotes: 1

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