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Postgresql select into temp table11/8/2023 I do this by querying the sys.columns catalog view in the original database (for the original table) and in the tempdb database (for the temporary tables). In this example I compare the two temporary tables with the original table. In this example, I use WHERE 1 = 0 to return no data. Here’s an example of creating a table without data. You can also filter the data with a WHERE clause if you need to. Here’s an example of creating a temporary table based on a persistent table, and copying all data in the process. In other words, you can copy data from the original table if you wish, or you can create the table without any data. You can create the table with or without data. PHP's PostgreSQL handler ( not PDO) includes very basic pg_copy_from and pg_copy_to functions which copy to/from a PHP array, which may not be efficient for large data sets.In SQL Server you can create a temporary table based on another table by using the SELECT. Your application programming language may also have support for pushing or fetching the data, but you cannot generally use COPY FROM STDIN/ TO STDOUT within a standard SQL statement, because there is no way of connecting the input/output stream. Thus, file accessibility and access rights depend on the client rather than the server when \copy is used. \copy invokes COPY FROM STDIN or COPY TO STDOUT, and then fetches/stores the data in a file accessible to the psql client. Note that there is no terminating, because meta-commands are terminated by newline, unlike SQL commands.ĭo not confuse COPY with the psql instruction \copy. The psql command-line client has a special "meta-command" called \copy, which takes all the same options as the "real" COPY, but is run inside the client: \copy (Select * From foo) To '/tmp/test.csv' With CSV The underlying syntax for this is the COPY TO STDOUT command, and graphical tools like pgAdmin will wrap it for you in a nice dialog. The Postgres server doesn't need to know what file you're copying to, it just spits out the data and the client puts it somewhere. The other approach is to do the file handling on the client side, i.e. I've written a blog post expanding on this approach, including some examples of functions that export (or import) files and tables meeting strict conditions. You probably don’t want to let someone invoke your function and add rows on the end of your “users” table… Which tables should the user be able to read/write in the database? This would normally be defined by GRANTs in the database, but the function is now running as a superuser, so tables which would normally be "out of bounds" will be fully accessible.Which files should the user be allowed to read/write on disk? This might be a particular directory, for instance, and the filename might have to have a suitable prefix or extension.The crucial part is that your function is there to perform additional checks, not just by-pass the security - so you could write a function which exports the exact data you need, or you could write something which can accept various options as long as they meet a strict whitelist. That doesn't actually mean you have to be connected as a superuser (automating that would be a security risk of a different kind), because you can use the SECURITY DEFINER option to CREATE FUNCTION to make a function which runs as though you were a superuser. It also needs to be run as a Postgres "superuser" (normally called "root") because Postgres can't stop it doing nasty things with that machine's local filesystem. This approach runs entirely on the remote server - it can't write to your local PC. Copy (Select * From foo) To '/tmp/test.csv' With CSV DELIMITER ',' HEADER If you want something easy to re-use or automate, you can use Postgresql's built in COPY command. I wish it would just create the structure automatically like it does in SQL.ĭo you want the resulting file on the server, or on the client? Server side I don't want to declare my temporary table structure, though. It seems like SELECT INTO works differently in PL/pgSQL, because you can select into the variables you've declared. Does anyone have any explanation for why this doesn't work inside a function? The PostgreSQL usage of SELECT INTO to represent table creation is historical. This indeed is the usage found in ECPG (see Chapter 35) and PL/pgSQL (see Chapter 42 ). SELECT INTO is really simple – automatically creating a table of the same structure of the SELECT query. The SQL standard uses SELECT INTO to represent selecting values into scalar variables of a host program, rather than creating a new table. I can SELECT INTO a variable of type record within PL/pgSQL, but then I have to define the structure when getting data out of that record. This statement creates a table called mytable (If orig_table exists as a relation): SELECT *īut put this function into PostgreSQL, and you get the error: ERROR: "temp" is not a known variable CREATE OR REPLACE FUNCTION whatever() SELECT INTO works in SQL but not PL/pgSQL. I want to use SELECT INTO to make a temporary table in one of my functions.
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