I'm trying to run the following SQL statement that is taking too long to finish in Oracle.
Here is my query:
SELECT timestamp from data
WHERE (timestamp IN
(SELECT MIN (timestamp) FROM data
WHERE (( TIMESTAMP BETWEEN :t1 AND :t2))
If anyone can help with optimising this query I would be very grateful.
All you need to speed your query is an index on timestamp:
create index data_timestamp on data(timestamp);
If you are expecting only one result, you can also do:
SELECT MIN(timestamp)
FROM data
WHERE TIMESTAMP BETWEEN :t1 AND :t2
I'm not sure why you would want to output the timestamp multiple times.
Related
we have a database that is growing every day. roughly 40M records as of today.
This table/database is located in Azure.
The table has a primary key 'ClassifierID', and the query is running on this primary key.
The primary key is in the format of ID + timestamp (mmddyyy HHMMSS), for example 'CNTR00220200 04052021 073000'
Here is the query to get all the IDs by date
**Select distinct ScanID
From ClassifierResults
Where ClassifierID LIKE 'CNTR%04052020%**
Very simple and straightforward, but it sometimes takes over a min to complete. Do you have any suggestion how we can optimize the query? Thanks much.
The best thing here would be to fix your design so that a) you are not storing the ID and timestamp in the same text field, and b) you are storing the timestamp in a proper date/timestamp column. Using your single point of data, I would suggest the following table design:
ID | timestamp
CNTR00220200 | timestamp '2021-04-05 07:30:00'
Then, create an index on (ID, timestamp), and use this query:
SELECT *
FROM yourTable
WHERE ID LIKE 'CNTR%' AND
timestamp >= '2021-04-05' AND timestamp < '2021-04-06';
The above query searches for records having an ID starting with CNTR and falling exactly on the date 2021-04-05. Your SQL database should be able to use the composite index I suggested above on this query.
I just want to know if it's possible to use date_trunc function for postgresql? Because I have a table that contains time without time zone.
example: SELECT date_trunc('hour', time 'columnName') from tableName
Thank you so much! Keep safe everyone
I'm looking to be able to create a table that contains all of the dates (inclusive) between the min and max date from another table. See below the simple query to get these dates
-- Get the min and max dates from the table
select min(date(sale_date)) as min_date,
max(date(sale_date)) as max_date
from TABLE;
I've spent the last hour googling this problem and have found attempts at doing this on MySQL and Oracle SQL but not on Hive SQL which I've been unable to convert to Hive SQL. If anyone has any idea on how to do this, please let me know. Thanking you in advance.
Ok this isn't my answer. A colleague was able to answer it. Still I think its important that I show my colleague's solution for your future benefit. It assumes that you've created a table that contains the min date and max date.
CREATE TABLE TABLE_2
STORED AS AVRO
LOCATION 'xxxxxx'
AS
SELECT date_add (t.min_date,pe.i) AS date_key
FROM TABLE_1 t
LATERAL VIEW
posexplode(split(space(datediff(t.max_date,t.min_date)),' ')) pe AS i,x;
i am trying to count the number of records in the particular date.
eventually, got the query worked but confused between these two queries which seemed to same for me. why should i enclose the date_time instead of quote in the conversion.
when i hit the query,
select count(*) from TABLENAME
where FROM_UNIXTIME(UNIX_TIMESTAMP(date_time), 'yyyyMMdd')='20170312';
result is count of the particular date is arrived.
but when i hit,
select count(*) from TABLENAME
where FROM_UNIXTIME(UNIX_TIMESTAMP('date_time', 'yyyyMMdd'))='20170312';
the result is 0.
please explain the difference of these queries.
date_time is a column while 'date_time' is a string and the attempt to use it as date result in NULL.
If you want to qualify the column name you should use `date_time`
I am querying a postgres database table that I only have read access to and cannot modify in any way. Long story short I need to run a query daily to pull records over several days. I have been going in each day and physically modifying the timestamp parameters. The table is about 40 million records and I am running pass through queries from a sql server to the linked server.
There is an index on the c_stime field which is a time stamp that I am trying to take advantage of, but when I perform a function over the field I kill that advantage. Here are some of my results:
select * from p_table where c_stime >= '2013-09-24 00:00:00.0000000'
select * from p_table where c_stime >= current_date::timestamp
select * from p_table where c_stime >= current_date+ interval '0 hour'
First one runs in 10 seconds, second runs in 74 seconds, third runs in 88 seconds. Want something dynamic like the second/third with performance close to the first. Any help appreciated
First, check your query plans. There may be surprises there.
Secondly, if the problem is as you say, I am surprised that this wouldn't have worked. However you can use the pg_catalog.* functions to convert types and these are immutable (allowing the function to be run before the query is planned), so you could try:
select * from p_table where c_stime >= pg_catalog.timestamp(current_date);