PostgreSQL table variable

问题:

Is there anything like table variables in T-SQL?
In Sql Server it looks like this:

DECLARE @ProductTotals TABLE
(
  ProductID int,
  Revenue money
)

Then in procedure I can:

INSERT INTO @ProductTotals (ProductID, Revenue)
  SELECT ProductID, SUM(UnitPrice * Quantity)
  FROM [Order Details]
  GROUP BY ProductID

And manipulate with this variable like an ordinary table.

Here is description: http://odetocode.com/Articles/365.aspx

回答1:

As @Clodoaldo commented: use a temporary table in PostgreSQL. For your example:

CREATE TEMP TABLE product_totals (
   product_id int
 , revenue money
);

More information in the manual about CREATE TABLE where you can find this quote:

If specified, the table is created as a temporary table. Temporary tables are automatically dropped at the end of a session, or optionally at the end of the current transaction (see ON COMMIT below). Existing permanent tables with the same name are not visible to the current session while the temporary table exists, unless they are referenced with schema-qualified names. Any indexes created on a temporary table are automatically temporary as well.

Unlogged tables are a somewhat related feature of PostgreSQL 9.1. They save disk writes by not writing to WAL. Here is a discussion of the features by Robert Haas.

Aside, concerning the money data type:

• PostgreSQL: Which Datatype should be used for Currency?

回答2:

You can you array of composite type instead

CREATE TABLE xx(a int, b int);

CREATE OR REPLACE FUNCTION bubu()
RETURNS void AS $$
DECLARE _x xx[];
BEGIN
   _x := ARRAY(SELECT xx FROM xx);
   RAISE NOTICE '_x=%', _x;
   ...