Creating Crosstab Pivot Table in PostgreSQL 9.0

Give this a try,tested on my machine

First make sure GROUP_CONCAT has plenty of space:

SET SESSION group_concat_max_len = 1000000;

SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
    CONCAT(
      'COUNT(DISTINCT CASE WHEN buyer_country= ''',
      buyer_country,
      ''' THEN transactions.buyer_id END) AS ',
      buyer_country
    )
   )INTO @sql
FROM  transactions 
LEFT JOIN buyers on transactions.buyer_id=buyers.buyer_id;


SET @sql=CONCAT('SELECT transactions.seller_country,',@sql,' FROM  transactions 
LEFT JOIN buyers on transactions.buyer_id=buyers.buyer_id GROUP BY transactions.seller_country');



PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

Link

Edit

ALTER TABLE transactions ADD key trans_idx (buyer_id)
ALTER TABLE buyers ADD key buyers_idx (buyer_id)

Proper crosstab query

First of all, the presented query would not work while you still have char(n) in your table definition - like we discussed under your previous question. You would need to convert to text or varchar first.

This works with your current table definition:

SELECT * FROM crosstab(
   'SELECT postcode_nospace_::text, ageband::text, count(ageband) AS ct
    FROM   adult_social_care.activities_in_localities_asc
    GROUP  BY 1, 2
    ORDER  BY 1'

   ,$$VALUES ('18-24'::text), ('25-34'), ('35-44'), ('45-54'), ('55-64')
           , ('65-74'), ('75-84'), ('85-94'), ('95 AND OVER')$$
   )
AS t("postcode" text
   , "18-24" bigint, "25-34" bigint,"35-44" bigint, "45-54" bigint, "55-64" bigint
   , "65-74" bigint, "75-84" bigint, "85-94" bigint, "95 AND OVER" bigint);

I am also using bigint instead of numeric to save another unnecessary type conversion (count() returns bigint).

Detailed explanation:

• PostgreSQL Crosstab Query

Better table definition

But better ALTER the data type in your table to text like @dezso suggested. Or, if you want to keep the length limit, add a CHECK constraint or use varchar(n). Never use char(n).

ALTER TABLE activities_in_localities_asc
   ALTER COLUMN ageband TYPE varchar(12)
 , ALTER COLUMN postcode_nospace_ TYPE varchar(8);

 ALTER TABLE gazetteers_and_addresses.unit_postcode
   ALTER COLUMN pc_area TYPE varchar(10);

Then you don't need to cast original column values any more:

SELECT * FROM crosstab(
   'SELECT postcode_nospace_, ageband, count(ageband)
    ...

Ideally, though, ageband should be an enum or (my preference) an ID referencing a lookup table, not plain, error-prone text ... key word: normalization.

Add total count

Building on your table, but with text or varchar() columns.

Wrap your original query into a CTE and call the the result twice in a UNION query - the 2nd call adds totals per postcode:

SELECT * FROM crosstab(
  $$WITH cte AS (
      SELECT postcode_nospace_, ageband, count(ageband) AS ct
      FROM   adult_social_care.activities_in_localities_asc  
      GROUP  BY 1, 2
      )
   TABLE  cte  -- original results
   UNION ALL   -- add total per postcode
   SELECT postcode_nospace_, 'total' AS ageband, sum(ct) AS ct
   FROM   cte
   GROUP  BY 1
   ORDER  BY 1$$  -- dollar-quotes to include single quotes easily

   ,$$VALUES ('18-24'::text), ('25-34'), ('35-44'), ('45-54'), ('55-64')
           , ('65-74'), ('75-84'), ('85-94'), ('95 AND OVER'), ('total')$$
   )
AS t("postcode" text
   , "18-24" bigint, "25-34" bigint,"35-44" bigint, "45-54" bigint, "55-64" bigint
   , "65-74" bigint, "75-84" bigint, "85-94" bigint, "95 AND OVER" bigint, "total" bigint);

About the TABLE command:

• Is there a shortcut for SELECT * FROM in psql?

Related CTE examples:

• Combine results of two queries, where the second relies on the first
• Get n grouped categories and sum others into one