I have a table with a lot of rows and I want to create a new table and copy just a bunch of rows (like 30) in my new table....
- the table name is account (code,code_activation,email,password) and I'm using PostgreSQL.
You can use insert command:
INSERT INTO AccountCopy (SELECT code,code_activation,email,password FROM account LIMIT 30);
You can put a WHERE clause and select those rows that you want. LIMIT n select the first n rows of a table.
Related
I have a table in Postgres that has ~50 million rows. I need to convert certain columns to rows.
I need to unpivot certain columns for individuals that repeat as an individual column and repeat the non-individual variables against the respective ID -
The following is the output I need -
Id appreciate any help on this.
50 million rows is not a big deal in Greenplum but returning that many rows to a client is kind of pointless. I'm guessing you want to create a new table for this new output. You are also going to be creating a table that is 2x larger because you are taking a single row and turning it into 2.
create table new_table as
select id, mid_1 as mid, name_1 as name, age_1 as age, location
from your_table
union all
select id, mid_2 as mid, name_2 as name, age_2 as age, location
from your_table
distributed by (id);
We have a table having three indexed columns say
column1 of type bigint
column2 of type timestamp without time zone
column3 of type timestamp without time zone
The table is having more than 12 crores of records and we are trying to delete all the records which are greater than current date - 45 days using below query
delete from tableA
where column2 <= '2019-04-15 00:00:00.00'
OR column3 <= '2019-04-15 00:00:00.00';
This is executing for ever and never completes.
Is there any way we can improve the performance of this query.
Drop indexes, delete data and recreate indexes. But this is not working as I am not able to delete data even after dropping the indexes.
delete
from tableA
where column2 <= '2019-04-15 00:00:00.00'
OR column3 <= '2019-04-15 00:00:00.00'
I do not want to change the query but want the Postgres configured through some property so that it is able to delete the records
See also for a good discussion of the issue Best way to delete millions of rows by ID
12 crores == 120 million rows?
Deleting from a large indexed table is slow because the index is rebuilt many times during the process. If you can select the rows you want to keep and use them to create a new table, then drop the old one, the process is much faster. If you do this regularly, use table partitioning and disconnect a partition when required, this can then be dropped.
1) Check the logs, you are probably suffering from deadlocks.
2) Try creating a new table selecting the data you need, then drop and rename. Use all the columns in your index in the query. DROP TABLE is much faster than DELETE .. FROM
CREATE TABLE new_table AS (
SELECT * FROM old_table WHERE
column1 >= 1 AND column2 >= current_date - 45 AND column3 >= current_date - 45);
DROP TABLE old_table;
ALTER TABLE new_table RENAME TO old_table;
CREATE INDEX ...
3) Create a new table using partitions based on date, with a table for say 15, 30 or 45 days (if you regularly remove data that is 45 days old). See https://www.postgresql.org/docs/10/ddl-partitioning.html for details.
I am not able to select distinct store_id from the table in postgres..
Your syntax is wrong - try using DISTINCT ON (more info here)
If you want to maintain the column order you can do a nested select
I am currently trying to join two tables, where both of the tables have very many different in the columns I am joining.
Here's the tsql
from AVG(Position) as Position from MonitoringGsc_Keywords as sk
Join GSC_RankingData on sk.Id = GSC_RankingData.KeywordId
groupy by sk.Id
The execution plan shows me, that it takes very much time to perform the join. I think it is because a huge group from the first table has to be compared with a huge group of values in the second table.
MonitoringGsc_Keywords.Id has about 60.000 different values
GSC_RankingData hat about 100.000.000 Values
MonitoringGsc_Keywords.Id is Primary-Key of MonitoringGsc_Keywords GSC_RankingData.KeywordId is indexed.
So, what can i do to increase performance?
Is Position column from GSC_RankingData table? If yes then JOIN is redundant and query should looks like this:
SELECT AVG(rd.Position) as Position
FROM GSC_RankingData rd
GROUP BY rd.KeywordId;
If Position column is in GSC_RankingData table then index on GSC_RankingData should include this column and looks like this:
CREATE INDEX IX_GSC_RankingData_KeywordId_Position ON GSC_RankingData(KeywordId) INCLUDE(Position);
You should check indexes fragmentation for this tables, to do this you could use this query:
SELECT * FROM sys.dm_db_index_physical_stats(db_id(), object_id('MonitoringGsc_Keywords'), null, null, 'DETAILED')
if avg_fragmentation_in_percent > 5% and < 30% then
ALTER INDEX [index name] on [table name] REORGANIZE;
if avg_fragmentation_in_percent >= 30% then
ALTER INDEX [index name] on [table name] REBUILD;
It could be problem with statistics, you could check it with query:
SELECT
sp.stats_id, name, filter_definition, last_updated, rows, rows_sampled,
steps, unfiltered_rows, modification_counter
FROM sys.stats AS stat
CROSS APPLY sys.dm_db_stats_properties(stat.object_id, stat.stats_id) AS sp
WHERE stat.object_id = object_id('GSC_RankingData');
check last update date, rows count, if it not be current then update statistics. Also it could be possible that statistics not exist, then you must create it.
Good day,
I have a table with some records that should be deleted. I would like to keep track of the deleted records and place such records in a new table. I would like to do the following:
SELECT * INTO TEMP FROM TABLE WHERE criteria < 1;
And then delete these records with DELETE query. Later on I would like to do a new SELECT query:
SELECT * INTO TEMP FROM TABLE WHERE new_criteria > 2;
And then delete those records as well. I will be working from only one table and just place the selected records into the same, new table (just for reference).
Thanks!
INSERT INTO temp (SELECT * FROM tbl WHERE criteria < 1);
Does you temp table have the same structure as the original. if the temp does not exist you might want to do this.
create table temp as select * from TABLE where criteria <1
If you are using Postgresql 9.3 You could also do everything in one command:
WITH deleted_rows AS (
DELETE FROM tbl
WHERE criteria<1
RETURNING *
)
INSERT INTO temp
SELECT * FROM deleted_rows;
(see http://www.postgresql.org/docs/9.3/static/queries-with.html#QUERIES-WITH-MODIFYING )