I have decided in my table that I no longer want to record start and finish times, but rather just a start time and a duration in minutes. How can I update my table so that my new column has its values inserted based on the existing data? my attempt below yields the error:
You can't specify target table 'lesson' for update in FROM clause
UPDATE lesson
SET duration =
(SELECT TIME_TO_SEC(TIMEDIFF(finish_time,start_time))/60
FROM lesson AS l
WHERE l.id = lesson.id)
You dont have to do that because your updating a column with values of other columns in the same row, do just:
UPDATE lesson
SET duration = TIME_TO_SEC(TIMEDIFF(finish_time,start_time))/60
Related
i had query like this
CREATE TRIGGER `tambah_riwayatobat` AFTER INSERT ON `obat`
FOR EACH ROW insert into riwayat_obat(nama, keterangan, distributor,tanggal)
(select new.nama, 'Masuk', d.nama ,now()
From distributor d
join obat ON new.id_distributor = d.id_distributor)
i try to insert data with trigger and one of part data i fetch with constraint, but why the data be duplicate entry ?
Output :
example, if i try to insert data obat 1st time, data on tambah_riwayatobat insert 1 too
if i try to insert data obat 2nd time, data on tambah_riwayatobat insert 2 times with same data
if i try to insert data obat 3rd time, data on tambah_riwayatobat insert 3 times with same data
I'm not certain exactly what's happening, but it's a result of the join in your trigger code. You’re joining obat to distributor, but your join condition makes no mention of obat so you're getting some sort of cross-product where on the second and subsequent INSERT your SELECT subquery is selecting more than one row.
You shouldn't (and don't need to) use the join, since all the data you need from obat is already in the pseudorecord NEW. The following code should work much better:
CREATE TRIGGER `tambah_riwayatobat`
AFTER INSERT ON `obat`
FOR EACH ROW
INSERT INTO riwayat_obat
(nama, keterangan, distributor, tanggal)
(SELECT NEW.nama, 'Masuk', d.nama, now()
FROM distributor d
WHERE new.id_distributor = d.id_distributor
LIMIT 1);
The LIMIT clause will ensure that the SELECT selects only one row, so the INSERT inserts only one row; if distributor.id_distributor is a primary key the LIMIT clause is unnecessary.
I have two tables, Entries and mountPanels. What I want to do is when a record is inserted in mountPanels, sum up the panels in that table by the ID of the inserted record, and update the Entries table with that sum (that matches the same ID).
When I try the below AFTER INSERT trigger:
UPDATE Entries SET panels = (SELECT SUM(panels) FROM mountPanels WHERE Entries.EntryID = new.EntryID)
It sums up everything, but when I try
UPDATE Entries SET panels = (SELECT SUM(panels) FROM mountPanels WHERE Entries.EntryID = mountPanels.EntryID)
It sums up everything correctly by ID, but updates every row. I just want it to update the specific row with the ID that was entered last.
Your update statement doesn't have a where clause, so of course it's updating every row. Also, your statement doesn't seem to be using new correctly.
Try this:
UPDATE Entries SET
panels = (
SELECT SUM(panels)
FROM mountPanels
WHERE EntryID = new.EntryID)
WHERE EntryID = new.EntryID
How can I store only 10 rows in a MySQL table? The older rows should be deleted when a new row is added but only once the table has 10 rows.
Please help me
You could achieve this with an after insert trigger, delete the row where it is min date. e.g. DELETE FROM myTable WHERE myTimestamp = (SELECT MIN(myTimestamp) FROM myTable) but that could in theory delete multiple rows, depending on the granularity of your updates.
You could have an incrementing sequence, and always just delete the min of that sequence.
The question is why you'd want to do this though? It's a slightly unusual requirement.
A basic example (not validated/executed, I don't have mySQL on this particular machine) would look something like.
CREATE TRIGGER CycleOldPasswords AFTER INSERT ON UserPasswords FOR EACH ROW
set #mycount = SELECT COUNT(*) FROM UserPasswords up where up.UserId = NEW.UserId;
if myCount >= 10 THEN
DELETE FROM UserPasswords up where up.Timestamp = (SELECT min(upa Timestamp) FROM UserPasswords upa WHERE NEW.UserId = upa.UserId) AND NEW.UserId = up.UserId;
END
END;
You can retrieve the last inserted id when your first row is inserted, and store it in a variable. When 10 rows are inserted, delete the row having id < id of the first inserted record. Please try it.
first of all insert all values using your insert query
and then run this query
delete from table_name where (cond) order by id desc limit 10
must specify an id or time in one column
I have a query written very poorly in SQL Server 2008
UPDATE PatientChartImages
SET PatientChartImages.IsLockDown = #IsLockdown
WHERE PatientChartImages.IsLockDown = #IsNotLockdown
AND PatientChartId IN (
SELECT PatientCharts.PatientChartId
FROM PatientCharts
WHERE ( PatientCharts.ChartStatusID = #ChartCompletedStatusID
OR PatientCharts.ChartStatusID = #ChartOnBaseStatusID
)
AND PatientCharts.IsLockDown = #IsNotLockdown
AND PatientCharts.CompletedOn IS NOT NULL
AND DATEDIFF(MINUTE, PatientCharts.CompletedOn, GETUTCDATE()) >= ( SELECT
tf.LockUpInterval
FROM
#tblFacCOnf tf
WHERE
tf.facilityId = PatientCharts.FacilityId
) )
This query locks the main table and results in TimeOut. IF i create a CTE first of all the updateable records and then update the main table by joining to the CTE. Will it help ??
First thing i advice you to do is to substitute IN condition with EXISTS. Second is to move all this conditional logic into CTE. Third is to substitute sub-select with #tblFacCOnf with join.
Last advice depends on your business logic and is not so important in my opinion
So at the end you will get something as
WITH search_cte as (
SELECT PatientCharts.PatientChartId
FROM PatientCharts
JOIN #tblFacCOnf tf on tf.facilityId = PatientCharts.FacilityId
WHERE ( PatientCharts.ChartStatusID = #ChartCompletedStatusID
OR PatientCharts.ChartStatusID = #ChartOnBaseStatusID
)
AND PatientCharts.IsLockDown = #IsNotLockdown
AND PatientCharts.CompletedOn IS NOT NULL
AND DATEDIFF(MINUTE, PatientCharts.CompletedOn, GETUTCDATE()) >= tf.LockUpInterval
) --cte end
UPDATE PatientChartImages
SET PatientChartImages.IsLockDown = #IsLockdown
WHERE PatientChartImages.IsLockDown = #IsNotLockdown
AND EXISTS (select 1 from PatientChartImages where PatientChartImages.PatientChartId = search_cte.PatientChartId)
One additional thing I might suggest if the other suggestions don't get you enough speed is not to use a table variable. Temp Tables are often faster for large data sets and can be indexed if need be.
The update lock is being held the time it takes to compute the CTE and the time for the update. The CTE time is probably causing the time out.
To reduce the lock time to the minimum required to update the target table. I suggest you create a temp table with two columns. Col1 is the primary key or cluster key of the target table and Col2 is the value you want in the target table. Wrap the temp table creation and fill the table with values according to your business logic within a transaction. Update the target table using a join to the temp table and the value from the temp table in a seperate transaction. After update drop the temp table.
I think you should create an SQL script (or stored procedure, if you will use it from a higher level) where you store the results of your selection into a cursor (you'll only have to find the PatientCartId's of the rows to be updated) and then you should use it in your update, so, the answer is yes.
It's easy to test this, you should put these commands into a transaction, rollback the transaction and before the rollback you should perform a selection to test your results. Good luck.
I am confused about how to copy a column from one table to another table using where. I wrote SQL query but it says transaction lock time exceeded or query returns more than one row.
using mysql
Basically,
I have:
Table 1: Results
BuildID platform_to_insert
Table 2: build
BuildID correct_platform
update results set results.platform_to_insert
= (select correct_platform from
build where results.BuildID = build.BuildID)
I do not believe you need a sub query.
UPDATE results, build
SET results.platform_to_insert = build.correct_platform
WHERE results.BuildID = build.BuildID
There are two options here:
update your tables to use BuildID as a primary key (to avoid duplicates)
update your subquery to only return one result
UPDATE results SET results.platform_to_insert = (
SELECT correct_platform
FROM build
WHERE results.BuildID=build.BuildID LIMIT 1
);