Learn more. Asked 1 year, 7 months ago. Active 1 year, 7 months ago. Viewed times. I cant get my code to write a csv file from a postgres table. Any suggestions? Sam , that is fantastic information but a digression from the problem at hand.
Add a comment. Active Oldest Votes. Mahsa Hassankashi Mahsa Hassankashi 1, 1 1 gold badge 11 11 silver badges 25 25 bronze badges. You're not actually putting that file name into the SQL to execute. Block data copy from pen drive to Computer.
How to copy file from network drive to local drive using C? Layout: fixed fluid. Web03 2. Strip HTML. Encode HTML. Paste as-is. Code block. Quoted Text. Best guess. The signature is designed to allow easy identification of files that have been munged by a nonbit-clean transfer.
This signature will be changed by end-of-line-translation filters, dropped zero bytes, dropped high bits, or parity changes. Note that this field is stored in network byte order most significant byte first , as are all the integer fields used in the file format. Bits are reserved to denote critical file format issues; a reader should abort if it finds an unexpected bit set in this range. Bits are reserved to signal backwards-compatible format issues; a reader should simply ignore any unexpected bits set in this range.
Currently only one flag bit is defined, and the rest must be zero:. Currently, this is zero, and the first tuple follows immediately. Future changes to the format might allow additional data to be present in the header. A reader should silently skip over any header extension data it does not know what to do with. The header extension area is envisioned to contain a sequence of self-identifying chunks. The flags field is not intended to tell readers what is in the extension area.
Specific design of header extension contents is left for a later release. This design allows for both backwards-compatible header additions add header extension chunks, or set low-order flag bits and non-backwards-compatible changes set high-order flag bits to signal such changes, and add supporting data to the extension area if needed.
Each tuple begins with a bit integer count of the number of fields in the tuple. Presently, all tuples in a table will have the same count, but that might not always be true. Then, repeated for each field in the tuple, there is a bit length word followed by that many bytes of field data. The length word does not include itself, and can be zero. As a special case, -1 indicates a NULL field value.
No value bytes follow in the NULL case. Presently, all data values in a binary-format file are assumed to be in binary format format code one. It is anticipated that a future extension might add a header field that allows per-column format codes to be specified. It is a normal field except that it's not included in the field-count. In particular it has a length word — this will allow handling of 4-byte vs. The file trailer consists of a bit integer word containing This is easily distinguished from a tuple's field-count word.
A reader should report an error if a field-count word is neither -1 nor the expected number of columns. This provides an extra check against somehow getting out of sync with the data. The following example copies a table to the client using the vertical bar as the field delimiter:.
The following is the same data, output in binary format. The data is shown after filtering through the Unix utility od -c. The table has three columns; the first has type char 2 , the second has type text , and the third has type integer.
All the rows have a null value in the third column. The following syntax was used before PostgreSQL version 9. The following syntax was used before PostgreSQL version 7. It puts the focus on the query, hiding the boilerplate. The above becomes:. It also accepts the query through standard input, allowing us to read a query stored in a file. Storing the extracted CSV is a matter of redirecting the output to a file:. With this, psql2csv can streamline some of your manual reporting work.
For instance, you might have a collection of SQL queries you use periodically. Throwing together a small script that runs them all through psql2csv is quite simple. It also has options to specify all of the COPY formatting options explained above for extra convenience. Through the --set or --variable -v for short option you can pass variables to the psql session that can be used in your queries either.
Unfortunately, this only works when passing the command through standard input, not through the --command or -c option:.
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