Select from a table variable

问题

I am trying to save the result of a SELECT query, pass it, and reuse it in another PL/pgSQL function:

DECLARE
  table_holder my_table; --the type of table_holder is my_table;
  result text;

BEGIN
  SELECT * INTO table_holder FROM table_holder ;

  result = another_function(table_holder);  
  return result;
END

The code for another_function(table_holder my_table), respectively:

BEGIN

  RETURN QUERY
  SELECT col FROM table_holder where id = 1;

END

Is it possible to run a SELECT query on a variable? If not, is there a way to get around this limitation?

I am using PostgreSQL 9.2.

回答1:

There are no "table variables" in plpgsql. That's something you would find in SQL Server.

Use a temporary table instead:

BEGIN

CREATE TEMP TABLE table_holder AS
SELECT * FROM table_holder
WHERE <some condition>
ORDER BY <some expression>
;
...

END

A temporary table exists for the lifetime of a session. To drop it at the end of the function (or an enclosing transaction) automatically use ON COMMIT DROP in the creation statement.

CREATE TEMP TABLE table_holder ON COMMIT DROP AS
SELECT ...

The temporary table is automatically visible to any other function in the same session (or transaction respectively).

One alternative would be to use cursors in plpgsql, like described in the manual here.

来源：https://stackoverflow.com/questions/17873735/select-from-a-table-variable