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Robust SQL Query Programming Approach

I need to resort to raw SQL where ORM crashes (using Django 1.7). The problem is that most queries end up with 80-90%. I cannot find a reliable and safe way to create queries without violating reuse.

Is string concatenation the only way out, i.e. builds strings without parameters without using conditions if-else, and then safely includes parameters using prepared statements (to avoid SQL injection). I want to follow a simple approach to the SQL template for my project instead of re-creating the mini ORM.

For example, consider this query:

SELECT id, name, team, rank_score
FROM
  ( SELECT id, name, team
    ROW_NUMBER() OVER (PARTITION BY team
                       ORDER BY count_score DESC) AS rank_score
    FROM 
      (SELECT id, name, team
       COUNT(score) AS count_score
       FROM people
       INNER JOIN scores on (scores.people_id = people.id)
       GROUP BY id, name, team
      ) AS count_table
  ) AS rank_table
WHERE rank_score < 3

How can I:

a) WHERE people
) INNER JOIN LEFT OUTER
c) COUNT SUM
d) OVER / PARTITION?

+4
1

, :

SELECT *
FROM  (
   SELECT p.person_id, p.name, p.team, sum(s.score)::int AS score
         ,rank() OVER (PARTITION BY p.team
                       ORDER BY sum(s.score) DESC)::int AS rnk
    FROM  person p
    JOIN  score  s USING (person_id)
    GROUP BY 1
   ) sub
WHERE  rnk < 3;

  • . . .

  • . , , .

  • "", , , rank(), row_number().

  • , people.people_id PK, GROUP BY.

  • - ,

PL/pgSQL

plpgsql, . a - c . d , .

CREATE OR REPLACE FUNCTION f_demo(_agg text       DEFAULT 'sum'
                               , _left_join bool  DEFAULT FALSE
                               , _where_name text DEFAULT NULL)
  RETURNS TABLE(person_id int, name text, team text, score int, rnk int) AS
$func$
DECLARE
   _agg_op  CONSTANT text[] := '{count, sum, avg}';  -- allowed functions
   _sql     text;
BEGIN

-- assert --
IF _agg ILIKE ANY (_agg_op) THEN
   -- all good
ELSE
   RAISE EXCEPTION '_agg must be one of %', _agg_op;
END IF;

-- query --
_sql := format('
SELECT *
FROM  (
   SELECT p.person_id, p.name, p.team, %1$s(s.score)::int AS score
         ,rank() OVER (PARTITION BY p.team
                       ORDER BY %1$s(s.score) DESC)::int AS rnk
    FROM  person p
    %2$s  score  s USING (person_id)
    %3$s
    GROUP BY 1
   ) sub
WHERE  rnk < 3
ORDER  BY team, rnk'
   , _agg
   , CASE WHEN _left_join THEN 'LEFT JOIN' ELSE 'JOIN' END
   , CASE WHEN _where_name <> '' THEN 'WHERE p.name LIKE $1' ELSE '' END
);

-- debug   -- quote when tested ok
-- RAISE NOTICE '%', _sql;

-- execute -- unquote when tested ok
RETURN QUERY EXECUTE _sql
USING  _where_name;   -- $1

END
$func$  LANGUAGE plpgsql;

:

SELECT * FROM f_demo();
SELECT * FROM f_demo('sum', TRUE, '%2');    
SELECT * FROM f_demo('avg', FALSE);
SELECT * FROM f_demo(_where_name := '%1_'); -- named param

SQL Fiddle

+4

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