I want to lock one record in a table.
The record is specified as "the next that has ID greater than..."
CREATE TABLE test (id number);
SELECT id
FROM (SELECT id
FROM test
WHERE id > 10
ORDER BY id)
WHERE ROWNUM = 1
FOR UPDATE;
This seems intuitive and easy. But it is not. Any ideas?
P.S.
I do need the existing query to remain the same because it is a cursor and there are several places that use this cursor's %rowtype.
I think you're going to need something like:
SELECT id
FROM test
WHERE id =
(SELECT MIN(id)
FROM test
WHERE id > 10)
FOR UPDATE;
Related
I have a test script that I'm beggining to play with. I'm getting stuck with something that seems simple.
I want to iterate through rows to fetch data from last row of result set to use only it.
procedure e_test_send
is
cursor get_rec is
select
id,
email_from,
email_to,
email_cc,
email_subject,
email_message
from test_email_tab;
begin
for rec_ in get_rec loop
ifsapp.send_email_api.send_html_email(rec_.email_to,rec_.email_from, rec_.email_subject, rec_.email_message);
end loop;
end e_test_send;
All I'm trying to do is send an email with a message and to a person from the last row only. This is a sample table that will grow in records. At the minute I have 2 rows of data in it, if I execute this procedure it will send 2 emails which is not the desired action.
I hope this makes sense.
Thanks
Do you know which row is the last row? The one with the MAX(ID) value? If so, then you could base cursor on a straightforward
SELECT id,
email_from,
email_to,
email_cc,
email_subject,
email_message
FROM test_email_tab
WHERE id = (SELECT MAX (id) FROM test_email_tab)
As it scans the same table twice, its performance will drop as number of rows gets higher and higher. In that case, consider
WITH
temp
AS
(SELECT id,
email_from,
email_to,
email_cc,
email_subject,
email_message,
ROW_NUMBER () OVER (ORDER BY id DESC) rn
FROM test_email_tab)
SELECT t.id,
t.email_from,
t.email_to,
t.email_cc,
t.email_subject,
t.email_message
FROM temp t
WHERE t.rn = 1
which does it only once; sorts rows by ID in descending order and returns the one that ranks as the "highest" (i.e. the last).
full disclosure this is part of a homework question but I have tried 6 different versions and I am stuck.
I am trying for find 1 manager every time the query runs. I.e I put the department id in and 1 name pops out. currently, I get all the names, multiple times. I have tried a nesting with an '=' not nesting, union, intersection, etc. I can get the manager id with a basic query, I just can't get the name. the current version looks like this:
select e.ename
from .emp e
where d.managerid in (select unique d.managerid
from works w, .dept d, emp e1
where d.did=1 and e1.eid=w.eid and d.did=w.did );
I realize its probably a really basic mistake that I am not seeing - any ideas?
Its not clear what do you mean get 1 menager any time. are it should be different menagers any time or the same?
Lest go throw your query:
you select all empolyes from table emp where manager_id in next query dataset
You get all managers for dep=1. The rest of tables and conditions are not influent on result dataset.
I theing did is primary key for table dept, If so your query may be rewritten to
select e.ename
from emp e
where d.managerid in (select unique d.managerid
from dept d
where d.did=1);
but this query return to you all emploees and not manager from dept=1
and if you need a manager. you should get emploee who is a manager. If eid is primary key of employee, and managerid is id from employee table you need something like:
select e.ename
from emp e
where e1.eid in (select unique d.managerid
from dept d
where d.did=1);
I have a table with >1M rows of data and 20+ columns.
Within my table (tableX) I have identified duplicate records (~80k) in one particular column (troubleColumn).
If possible I would like to retain the original table name and remove the duplicate records from my problematic column otherwise I could create a new table (tableXfinal) with the same schema but without the duplicates.
I am not proficient in SQL or any other programming language so please excuse my ignorance.
delete from Accidents.CleanedFilledCombined
where Fixed_Accident_Index
in(select Fixed_Accident_Index from Accidents.CleanedFilledCombined
group by Fixed_Accident_Index
having count(Fixed_Accident_Index) >1);
You can remove duplicates by running a query that rewrites your table (you can use the same table as the destination, or you can create a new table, verify that it has what you want, and then copy it over the old table).
A query that should work is here:
SELECT *
FROM (
SELECT
*,
ROW_NUMBER()
OVER (PARTITION BY Fixed_Accident_Index)
row_number
FROM Accidents.CleanedFilledCombined
)
WHERE row_number = 1
UPDATE 2019: To de-duplicate rows on a single partition with a MERGE, see:
https://stackoverflow.com/a/57900778/132438
An alternative to Jordan's answer - this one scales better when having too many duplicates:
#standardSQL
SELECT event.* FROM (
SELECT ARRAY_AGG(
t ORDER BY t.created_at DESC LIMIT 1
)[OFFSET(0)] event
FROM `githubarchive.month.201706` t
# GROUP BY the id you are de-duplicating by
GROUP BY actor.id
)
Or a shorter version (takes any row, instead of the newest one):
SELECT k.*
FROM (
SELECT ARRAY_AGG(x LIMIT 1)[OFFSET(0)] k
FROM `fh-bigquery.reddit_comments.2017_01` x
GROUP BY id
)
To de-duplicate rows on an existing table:
CREATE OR REPLACE TABLE `deleting.deduplicating_table`
AS
# SELECT id FROM UNNEST([1,1,1,2,2]) id
SELECT k.*
FROM (
SELECT ARRAY_AGG(row LIMIT 1)[OFFSET(0)] k
FROM `deleting.deduplicating_table` row
GROUP BY id
)
Not sure why nobody mentioned DISTINCT query.
Here is the way to clean duplicate rows:
CREATE OR REPLACE TABLE project.dataset.table
AS
SELECT DISTINCT * FROM project.dataset.table
If your schema doesn’t have any records - below variation of Jordan’s answer will work well enough with writing over same table or new one, etc.
SELECT <list of original fields>
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY Fixed_Accident_Index) AS pos,
FROM Accidents.CleanedFilledCombined
)
WHERE pos = 1
In more generic case - with complex schema with records/netsed fields, etc. - above approach can be a challenge.
I would propose to try using Tabledata: insertAll API with rows[].insertId set to respective Fixed_Accident_Index for each row.
In this case duplicate rows will be eliminated by BigQuery
Of course, this will involve some client side coding - so might be not relevant for this particular question.
I havent tried this approach by myself either but feel it might be interesting to try :o)
If you have a large-size partitioned table, and only have duplicates in a certain partition range. You don't want to overscan nor process the whole table. use the MERGE SQL below with predicates on partition range:
-- WARNING: back up the table before this operation
-- FOR large size timestamp partitioned table
-- -------------------------------------------
-- -- To de-duplicate rows of a given range of a partition table, using surrage_key as unique id
-- -------------------------------------------
DECLARE dt_start DEFAULT TIMESTAMP("2019-09-17T00:00:00", "America/Los_Angeles") ;
DECLARE dt_end DEFAULT TIMESTAMP("2019-09-22T00:00:00", "America/Los_Angeles");
MERGE INTO `gcp_project`.`data_set`.`the_table` AS INTERNAL_DEST
USING (
SELECT k.*
FROM (
SELECT ARRAY_AGG(original_data LIMIT 1)[OFFSET(0)] k
FROM `gcp_project`.`data_set`.`the_table` AS original_data
WHERE stamp BETWEEN dt_start AND dt_end
GROUP BY surrogate_key
)
) AS INTERNAL_SOURCE
ON FALSE
WHEN NOT MATCHED BY SOURCE
AND INTERNAL_DEST.stamp BETWEEN dt_start AND dt_end -- remove all data in partiion range
THEN DELETE
WHEN NOT MATCHED THEN INSERT ROW
credit: https://gist.github.com/hui-zheng/f7e972bcbe9cde0c6cb6318f7270b67a
Easier answer, without a subselect
SELECT
*,
ROW_NUMBER()
OVER (PARTITION BY Fixed_Accident_Index)
row_number
FROM Accidents.CleanedFilledCombined
WHERE TRUE
QUALIFY row_number = 1
The Where True is neccesary because qualify needs a where, group by or having clause
Felipe's answer is the best approach for most cases. Here is a more elegant way to accomplish the same:
CREATE OR REPLACE TABLE Accidents.CleanedFilledCombined
AS
SELECT
Fixed_Accident_Index,
ARRAY_AGG(x LIMIT 1)[SAFE_OFFSET(0)].* EXCEPT(Fixed_Accident_Index)
FROM Accidents.CleanedFilledCombined AS x
GROUP BY Fixed_Accident_Index;
To be safe, make sure you backup the original table before you run this ^^
I don't recommend to use ROW NUMBER() OVER() approach if possible since you may run into BigQuery memory limits and get unexpected errors.
Update BigQuery schema with new table column as bq_uuid making it NULLABLE and type STRING
Create duplicate rows by running same command 5 times for example
insert into beginner-290513.917834811114.messages (id, type, flow, updated_at) Values(19999,"hello", "inbound", '2021-06-08T12:09:03.693646')
Check if duplicate entries exist
select * from beginner-290513.917834811114.messages where id = 19999
Use generate uuid function to generate uuid corresponding to each message
UPDATE beginner-290513.917834811114.messages
SET bq_uuid = GENERATE_UUID()
where id>0
Clean duplicate entries
DELETE FROM beginner-290513.917834811114.messages
WHERE bq_uuid IN
(SELECT bq_uuid
FROM
(SELECT bq_uuid,
ROW_NUMBER() OVER( PARTITION BY updated_at
ORDER BY bq_uuid ) AS row_num
FROM beginner-290513.917834811114.messages ) t
WHERE t.row_num > 1 );
A weird request maybe but. My boss wants me to create an admin version of a page we have that displays data from an oracle query in a table.
The admin page, instead of displaying the data (query returns 1 row), needs to return the table name and column name
Ex: Instead of:
Name Initial
==================
Bob A
I want:
Name Initial
============================
Users.FirstName Users.MiddleInitial
I realize I can do this in code but would rather just modify the query to return the data I want so I can leave the report generation code mostly alone.
I don't want to do it in a stored procedure.
So when I spit out the data in the report using something like:
blah blah = MyDataRow("FirstName")
I can leave that as is but instead of it displaying "BOB" it would display "Users.FirstName"
And I want to do the query using select * if possible instead of listing all the columns
So for each of the columns I am querying in the * , I want to get (instead of the column value) the tablename.ColumnName or tablename|columnName
hope you are following- I am confusing myself...
pseudo:
select tablename + '.' + Columnname as WhateverTheColumnNameIs
from Table1
left join Table2 on whatever...
Join Table_Names on blah blah
Whew- after writing all this I think I will just do it on the code side.
But if you are up for it maybe a fun challenge
Oracle does not provide an authentic way(there is no pseudocolumn) to get the column name of a table as a result of a query against that table. But you might consider these two approaches:
Extract column name from an xmltype, formed by passing cursor expression(your query) in the xmltable() function:
-- your table
with t1(first_name, middle_name) as(
select 1,2 from dual
), -- your query
t2 as(
select * -- col1 as "t1.col1"
--, col2 as "t1.col2"
--, col3 as "t1.col3"
from hr.t1
)
select *
from ( select q.object_value.getrootelement() as col_name
, rownum as rn
from xmltable('//*'
passing xmltype(cursor(select * from t2 where rownum = 1))
) q
where q.object_value.getrootelement() not in ('ROWSET', 'ROW')
)
pivot(
max(col_name) for rn in (1 as "name", 2 as "initial")
)
Result:
name initial
--------------- ---------------
FIRST_NAME MIDDLE_NAME
Note: In order for column names to be prefixed with table name, you need to list them
explicitly in the select list of a query and supply an alias, manually.
PL/SQL approach. Starting from Oracle 11g you could use dbms_sql() package and describe_columns() procedure specifically to get the name of columns in the cursor(your select).
This might be what you are looking for, try selecting from system views USER_TAB_COLS or ALL_TAB_COLS.
For example, I have a table tbl like
values
10
20
30
40
on this table by the condition I have GROUP BY like this:
SELECT ???
FROM tbl
GROUP BY values
I need to check that group has some value, for example 30
UPD:
In real task a have a table with many columns and other operations on them and in one column i need to check whether value in every group of this column.
UPD2:
I need something like this:
select
min(created_timestamp),
max(resource_id),
max(price),
CASE WHEN event_type has (1704 or 1701 or 1703) THEN return found value END
CASE WHEN event_type has (1707) THEN return 1707 END
from subscriptions
group by guid
SELECT
MIN(created_timestamp),
MAX(resource_id),
MAX(price),
MIN(CASE WHEN event_type IN (1704, 1701, 1703)
THEN found_value
WHEN event_type = 1707
THEN 1707
ELSE NULL
END)
FROM subscriptions
GROUP BY guid ;
I did not get what you have in the select clause .. but if you want to see the values also in the out put when you run the group by query try this
select function(), values from tbl group by values
function() -- could be any function like -- count or sum
and if you want only specific to value 30 .. then add a where clause values = 30.
You dont need to use group by clause if your aim is to find if some value exists.
Use this method if you also consider the performance.
SELECT DECODE (COUNT(1),0,'Not Exist','Yes has some values')
FROM dual
WHERE EXISTS ( SELECT 1
FROM tbl
WHERE VALUES='&Your_Value_To_Check'
)