I am trying to copy a table in a postgresql database (version 10.12) via psql. One of the rows contains strings representing xml data. When I query the database for a row count with this query I get a count of about 50,000:
select count(column) from table;
But when I try to export the data to a csv file the output has more than 1,000,000 rows! I don't understand how a csv export could have a different number of rows than the table!
This is the copy command:
\copy (select column from table) to 'directory/output.csv' with csv;
It doesn't seem to matter if I change the delimiter or quote either. I've tried using | as a delimiter and ` as a quote and the number of rows in the csv was the same. Why is the row count different in the csv export?
The row count is not different: the CSV output simply has linefeeds (LF, ASCII code 10) embedded in fields, which is expected in XML.
If you want one line per row with COPY, don't use CSV, use the text format, that is, just omit with csv. Then newlines are encoded with \n instead of being output verbatim.
Related
I'm was able to export data from Postgres to AWS S3 using this document by using the aws_commons extension.
The table columns are id and name. with this table I was able to export as csv file using below mentioned query
SELECT * from aws_s3.query_export_to_s3('select * from sample_table',
aws_commons.create_s3_uri('rds-export-bucket', 'rds-export', 'us-east-1') ,
options :='format csv , HEADER true'
);
with the query I'm able to generate csv file like
id,name
1,Monday
2,Tuesday
3,Wednesday
but is it possible to generate the csv file in the below mentioned format
id:1,name:Monday
id:2,name:Tuesday
id:3,name:Wednesday
I tried to create a different table with jsonb structure, and each row inserted as a json. then export had curly braces and two double quotes in it.
Sample insertion command,
CREATE TABLE unstructured_table (data JSONB NOT NULL);
INSERT INTO unstructured_table VALUES($$
{
"id": "1",
"name": "test"
}}
$$);
after exporting from this table, I'm getting csv file like,
"{""id"": ""1"", ""name"": "test"}"
Thanks in advance
JSON requires double quotes around strings and CSV also requires double quotes around fields when they contain commas or double quotes.
If your goal is to produce a comma-separated list of ColumnName:ColumnValue, for all columns and rows without any kind of quoting, then this requirement is not compatible with the CSV format.
This could however be generated in SQL relatively generically, for all columns and rows of any sample_table, id being the primary key, with a query like this:
select string_agg(k||':'||v, ',')
from sample_table t,
lateral row_to_json(t) as r(j),
lateral json_object_keys(j) as keys(k),
lateral (select j->>k) as val(v)
group by id order by id;
If you feed that query to aws_s3.query_export_to_s3 with a format csv option, it will enclose each output line with double quotes. That may be close enough to your goal.
Alternatively, the text format could be used. Then the lines would not be enclosed with double quotes, but backslashes sequences might be emitted for control characters and backslashes themselves (see the text format in the COPY documentation).
Ideally the result of this query should be output verbatim into a file, not using COPY, as you would do locally in a shell with:
psql -Atc "select ..." > output-file.txt
But it doesn't seem like aws_s3.query_export_to_s3 provides an equivalent way to do that, since it's an interface on top of the COPY command.
I have a CSV file with 12 - 11 - 10 or 5 columns.
After creating a PostgreSQL table with 12 columns, I want to copy this CSV into the table.
I use this request:
COPY absence(champ1, champ2, num_agent, nom_prenom_agent, code_gestion, code_service, calendrier_agent, date_absence, code_absence, heure_absence, minute_absence, periode_absence)
FROM 'C:\temp\absence\absence.csv'
DELIMITER '\'
CSV
My CSV file contains 80000 line.
Ex :
20\05\ 191\MARKEY CLAUDIE\GA0\51110\39H00\21/02/2020\1471\03\54\Matin
21\05\ 191\MARKEY CLAUDIE\GA0\51110\39H00\\8130\7H48\Formation avec repas\
30\05\ 191\MARKEY CLAUDIE\GA0\51430\39H00\\167H42\
22\9993\Temps de déplacement\98\37
when I execute the request, I get a message indicating that there is missing data for the lines with less than 12 fields.
Is there a trick?
copy is extremely fast and efficient, but less flexible because of that. Specifically it can't cope with files that have a different number of "columns" for each line.
You can either use a different import tool, or if you want to stick to built-in tools, copy the file into staging table that only has a single column, then use Postgres string functions to split the lines into the columns:
create unlogged table absence_import
(
line text
);
\COPY absence_import(line) FROM 'C:\temp\absence\absence.csv' DELIMITER E'\b' CSV
E'\b' is the "backspace" character which can't really appear in a text file, so no column splitting is taking place.
Once you have imported the file, you can split the line using string_to_array() and the insert that into the real table:
insert into absence(champ1, champ2, num_agent, nom_prenom_agent, code_gestion, code_service, calendrier_agent, date_absence, code_absence, heure_absence, minute_absence, periode_absence)
select line[1], line[2], line[3], .....
from (
select string_to_array(line, '\') as line
from absence_import
) t;
If there are non-text columns, might need to cast the values to the target data type explicitly: e.g. line[3]::int.
You can add additional expressions to deal with missing columns, e.g. something like: coalesce(line[10], 'default value')
Is there query equivalent to sql server's openquery or openrowset to use in postgresql to query from excel or csv ?
You can use PostgreSQL's COPY
As per doc:
COPY moves data between PostgreSQL tables and standard file-system
files. COPY TO copies the contents of a table to a file, while COPY
FROM copies data from a file to a table (appending the data to
whatever is in the table already). COPY TO can also copy the results
of a SELECT query
COPY works like this:
Importing a table from CSV
Assuming you already have a table in place with the right columns, the command is as follows
COPY tblemployee FROM '~/empsource.csv' DELIMITERS ',' CSV;
Exporting a CSV from a table.
COPY (select * from tblemployee) TO '~/exp_tblemployee.csv' DELIMITERS ',' CSV;
Its important to mention here that generally if your data is in unicode or need strict Encoding, then Always set client_encoding before running any of the above mentioned commands.
To set CLIENT_ENCODING parameter in PostgreSQL
set client_encoding to 'UTF8'
or
set client_encoding to 'latin1'
Another thing to guard against is nulls, while exporting , if some fields are null then PostgreSQL will add '/N' to represent a null field, this is fine but may cause issues if you are trying to import that data in say SQL server.
A quick fix is modify the export command by specifying what would you prefer as a null placeholder in exported CSV
COPY (select * from tblemployee ) TO '~/exp_tblemployee.csv' DELIMITERS ',' NULL as E'';
Another common requirement is import or export with the header.
Import CSV to table with Header for columns present in first row of csv file.
COPY tblemployee FROM '~/empsource.csv' DELIMITERS ',' CSV HEADER
Export a table to CSV with Headers present in the first row.
COPY (select * from tblemployee) TO '~/exp_tblemployee.csv' DELIMITERS ',' CSV HEADER
I am importing a csv file into postgres, and would like to know how to import the correct data type while using the COPY command. For instance, I have a column column_1 integer; and want to insert the value 6 into it from my csv file.
I run the command copy "Table" from 'path/to/csv' DELIMITERS ',' CSV; and every time I try to do this I get the error ERROR: invalid input syntax for integer: "column_1". I figured out that it's because it is automatically importing every piece of data from the csv file as a string or text. If I change the column type to text then it works successfully, but this defeats the purpose of using a number as I need it for various calculations. Is there a way to conserve the data type when transferring? Is there something I need to change in the csv file? Or is there another datatype to assign to column_1? Hope this makes sense. Thanks in advance!
I did this and it worked flawlessly:
I put the plain number in the stack.csv
(The stack.csv has only one value 6)
# create table stack(i int);
# \copy stack from 'stack.csv' with (format csv);
I read in your comment that you have 25 columns in your CSV file. You need to have at least 25 columns in your table. All columns need to be mapped from CSV. If you have more than 25 columns in table you need the map only the columns mapped from CSV.
That's why it works at a text field because all data is put in one row cell.
If you have more columns that "fields" in your CSV file than the format is like this
\copy stack(column1, column2, ..., column25) from 'stack.csv' with (format csv);
I have created a table in my database with name 'con' which has two columns with the name 'date' and 'kgs'. I am trying to extract data from this 'hi.rpt' file copied on this location 'H:Sir\data\reporting\hi.rpt' and want to store values in the table 'con' in my database.
I have tried this code in pgadmin
When I run:
COPY con (date,kgs)
FROM 'H:Sir\data\reporting\hi.rpt'
WITH DELIMITER ','
CSV HEADER
date AS 'Datum/Uhrzeit'
kgs AS 'Summe'
I get the error:
ERROR: syntax error at or near "date"
LINE 5: date AS 'Datum/Uhrzeit'
^
********** Error **********
ERROR: syntax error at or near "date"
SQL state: 42601
Character: 113
"hi.rpt" file from which i am reading the data look like this:
Datum/Uhrzeit,Sta.,Bez.,Unit,TBId,Batch,OrderNr,Mat1,Total1,Mat2,Total2,Mat3,Total3,Mat4,Total4,Mat5,Total5,Mat6,Total6,Summe
41521.512369(04.09.13 12:17:48),TB01,TB01,005,300,9553,,2,27010.47,0,0.00,0,0.00,3,1749.19,0,0.00,0,0.00,28759.66
41521.547592(04.09.13 13:08:31),TB01,TB01,005,300,9570,,2,27057.32,0,0.00,0,0.00,3,1753.34,0,0.00,0,0.00,28810.66
Is it possible to extract only two data values from 20 different type of data that i have in this 'hi.rpt' file or not?
or is there only a mistake in the syntax that i have written?
What is the correct way to write it?
I don't know where you got that syntax, but COPY doesn't take a list of column aliases like that. See the help:
COPY table_name [ ( column_name [, ...] ) ]
FROM { 'filename' | PROGRAM 'command' | STDIN }
[ [ WITH ] ( option [, ...] ) ]
(AS isn't one of the listed options; to see the full output run \d copy in psql, or look at the manual for the copy command online).
There is no mapping facility in COPY that lets you read only some columns of the input CSV. It'd be really useful, but nobody's had the time/interest/funding to implement it yet. It's really only one of many data transform/filtering tasks people want anyway.
PostgreSQL expects the column-list given in COPY to be in the same order, left-to-right, as what's in the CSV file, and have the same number of entries as the CSV file has columns. So if you write:
COPY con (date,kgs)
then PostgreSQL will expect an input CSV with exactly two columns. It'll use the first csv column for the "date" table column and the second csv column for the "kgs" table column. It doesn't care what the CSV headers are, they're ignored if you specify WITH (FORMAT CSV, HEADER ON), or treated as normal data rows if you don't specify HEADER.
PostgreSQL 9.4 adds FROM PROGRAM to COPY, so you could run a shell command to read the file and filter it. A simple Python or Perl script would do the job.
If it's a small file, just open a copy in the spreadsheet of your choice as a csv file, delete the unwanted columns, and save it, so only the date and kgs columns remain.
Alternately, COPY to a staging table that has all the same columns as the CSV, then do an INSERT INTO ... SELECT to transfer just the wanted data into the real target table.