In SQLite is it possible to move a whole row of a table to another table in one query, rather than selecting the row then inserting it into another table then deleting the row in the original table (3 query's)
well i am not sure about doing all 3 in one query but you can do the below for select and insert
Select column1, column2 into tableName
and then your delete
Related
We have a table in our db with copied data that has completely duplicated many rows. Because the id is also duplicated there is nothing we can use to select just the duplicates. I tried using a limit to only delete 1 but redshift gave a syntax error when trying to use limit.
Any ideas how we can delete just one of two rows that have completely identical information?
Use select distinct to create a new table. Then either truncate & copy the data, or drop the original table and rename the new table to the original name:
create table t2 as select distinct * from t;
truncate t;
insert into t from select * from t2;
drop table t2;
Add column a column with unique values. identity(seed, step) looks interesting.
I have two tables. One of them is a temporary table in which I copy the data from a big CSV file. After that I update my other table with the temporary table (see this answer: Copy a few of the columns of a csv file into a table).
When I update my temporary table once more with a (updated) CSV file (data from a grep in bash, increasing row numbers per update) I want to delete the rows that are not affected by the update. I could have a temp table smaller than a temp table with all the data.
First: Is it better drop all data in the temp table and to fill it with the whole updated CSV data and after that to update/insert the other table.
Second: Or to update the temp table in the first place?
So it is a matter of size of the tables. I talking about 500k rows (with geometry columns).
An example:
table
1, NULL
2, NULL
temp table
1, hello
2, good morning
CSV
1, hello there
2, good morning
3, good evening
temp table
1, hello there
2, good morning
3, good evening
OR
temp table
1, hello there
3, good evening
So my question is how to update a table with a CSV file, insert new rows, update the old rows and delete the rows that were not affected by the update.
So my question is how to update a table with a CSV file, insert new rows, update the old rows and delete the rows that were not affected by the update.
I see two possible solutions:
1. Apply the changes individually
The data is applied with a series of update/delete/insert statements like this:
-- get rid of deleted rows
delete from the_table
where not exists (select 1
from temp_table tt
where tt.id = the_table.id);
-- update changed data
update the_table
set ..
from temp_table src
where src.id = the_table.id;
-- insert new rows
insert into the_table
select ..
from temp_table src
where not exists (select 1
from the_table t2
where t2.id = src.id);
This is the required approach if other sources write to the target table and you don't want to overwrite that. Maybe you don't even want to delete "missing" rows then. Or update only a sub-set of the columns.
2. Flush and fill the table
If you never modify the data in the target table and you don't have foreign keys referencing that table, I would do a flush and fill of the real table:
truncate the_table;
copy the_table from '/path/to/data.csv' ...;
If you run the truncate and copy in a single transaction, the copy performance will improve because it minimizes the amount of WAL logging.
I haven't many experience with SQL(half year), but maybe you will compare your table using MINUS clause? Using MINUS you can get non-updated rows?
P.S. I'm talking about PL/SQL)
Below i have a table where i need to get fields from one column to three columns.
This is how i would like the data to end up
Column1
Music
Column2
com.sec.android.app.music
Column3
com.sec.android.app.music.MusicActionTabActivity
Give the table a numeric autonumber id
Remove the rows with no data with a select where blank spaces or null
Find records with no point in the content with a select
Use the previous query as a source and use the id to find the id + 1 to find the next record and do the same with + 2 to find the second row
Build a table to hold the new structure and use the query as a source to insert the new created data in the new table with the 3 columns structure.
This is an example using sql server
Test table design
Data in table
Query
Look at the query from the inside. The first query inside clean the null records. Then the second query find the records with out point. This records are the reference to find the related two records. Then the id of the records with out point are used to make a query in the select adding 1 for the next record and then other query adding 2 to find the other record. Now you only need to create a table to insert this data, using this query as the source.
My question is to simple, but I can't find out a way to delete old values of a table and update same table with results of same query.
UPDATE
The query is an SELECT on Table A, and the results be Table B. And nothing on Table B different of the result of last query on Table A.
I have a very big table, and I need to process the records and create a new table regularly. The old values of this table are not important, only the new ones.
I will appreciate any help.
What about a view? If you only need table B to query on. You said you have a select on table A. Lets say your select is SELECT * FROM TableA WHERE X = Y. Then your statement would be
CREATE VIEW vwTableB AS
SELECT * FROM TableA WHERE X = Y
And then instead of querying tableB you would query vwTableB. Any changes to the data in table A would be reflected in the view so you don't have to keep running a script yourself.
This was the data in vwTableB would be kept updated and you wouldn't have to keep deleting and inserting into the second table.
you can use a temporary table to store results you are working with, if you only need it for one session. it will automatically be dropped when you sign out.
you didn't say what db you are using, but try this
create temp tableB AS select * from tableA
In my table I have so many duplicate records
SELECT ENROLMENT_NO_DATE, COUNT(ENROLMENT_NO_DATE) AS NumOccurrences
FROM Import_Master GROUP BY ENROLMENT_NO_DATE HAVING ( COUNT(ENROLMENT_NO_DATE) > 1 )
I need to remove duplicate record if it is occur second time... Need to keep first or any of one record. How can I do that?
You can use CTE to perform this task:
;with cte as
(
select ENROLMENT_NO_DATE,
row_number() over(partition by ENROLMENT_NO_DATE order by ENROLMENT_NO_DATE) rn
from Import_Master
)
delete from cte where rn > 1
See SQL Fddle with Demo
One method could be to create a secondary, temporary table
CREATE TABLE Import_Master_Deduped AS SELECT * FROM Import_Master WHERE FALSE;
This will create an empty table with identical structure to Import_Master. Now impose uniqueness on the new table with an index:
CREATE UNIQUE INDEX Import_Master_Ndx ON Import_Master_Deduped(ENROLMENT_NO_DATE);
Finally copy the table with duplicated records inside with INSERT IGNORE, so that duplicated records will not get inserted:
INSERT IGNORE INTO Import_Master_Deduped SELECT * FROM Import_Master;
At this point, after checking everything is OK, you can rename the two tables swapping their names (this will lose any old indexes), or TRUNCATE the Import_Master table and copy back the deduped records from the new table into the old.
In the second case, recreate the UNIQUE constraint on the old table to avoid further duplicates; in the first, recreate any old indexes on the new table.
Finally, you remove the table you don't need anymore.