PostgreSQL，混合食物和食谱

Question

Before some time I had a problem which seem's to be solved but it is not so I have to explain it better and support with more suitable tables:

DROP TABLE IF EXISTS usedfood;  
CREATE TABLE usedfood 
   (food_code int, food_name text, qtyu integer, meas text);
INSERT INTO usedfood (food_code, food_name, qtyu, meas)
VALUES (10,  'spaghetti',        3, 'pcs'),
       (156, 'mayonnaise',       2, 'pcs'),
       (173, 'ketchup',          1, 'pcs'),
       (172, 'bolognese sauce',  2, 'pcs'),
       (173, 'ketchup',          1, 'pcs'),
       (175, 'worchester sauce', 2, 'pcs'),
       (177, 'parmesan',         1, 'pcs'),
       (10,  'spaghetti',        2, 'pcs'),
       (156, 'mayonnaise',       1, 'pcs');

DROP TABLE IF EXISTS ingredients;
CREATE TABLE ingredients
   (food_code int, ingr_code int, ingr_name text, qtyi decimal(11,3), meas text);
INSERT INTO ingredients (food_code, ingr_code, ingr_name, qtyi, meas)
VALUES (10,  1256, 'spaghetti rinf', 75, 'gramm'),
       (156, 1144, 'salt',          0.3, 'gramm'),
       (10,  1144, 'salt',          0.5, 'gramm'),
       (156, 1140, 'fresh egg',      50, 'gramm'),
       (172, 1138, 'tomato',         80, 'gramm'),
       (156, 1139, 'mustard',         5, 'gramm'),
       (172, 1136, 'clove',           1, 'gramm'),
       (156, 1258, 'oil',           120, 'gramm'),
       (172, 1135, 'laurel',        0.4, 'gramm'),
       (10,  1258, 'oil',           0.4, 'gramm'),
       (172, 1130, 'corned beef',    40, 'gramm');

Those two tables represent a list of food and list of ingredients used in SOME food.
However, some food haven't ingredients (and that is a prolem).

This query count and list usage of ingredients by list of food where food and ingredients are logically connected by 'food_code':

SELECT SUM(f.qtyu) AS used_times,
       COALESCE(i.ingr_code, MAX(f.food_code)) AS code,
       COALESCE(i.ingr_name, MAX(f.food_name)) AS f_name,
       SUM(COALESCE(i.qtyi, 1) * f.qtyu)::decimal(11,3) AS qty,
       COALESCE(max(i.meas), max(f.meas)) AS meas
  FROM usedfood f LEFT JOIN ingredients i
    ON f.food_code = i.food_code
 GROUP BY i.ingr_code, i.ingr_name

But here is issue that all food which haven't ingredients is grouped together instead of by code and is listed as one food. This is not wanted and I would like that some find and solve that problem to get this result from given tables:

 2   173 ketchup            2.000 pcs
 1   175 parmesan           1.000 pcs
 2   177 worchester sauce   2.000 pcs
 8  1144 salt               3.400 gramm
 3  1140 fresh egg        150.000 gramm
 2  1138 tomato           160.000 gramm
 8  1258 oil              362.000 gramm
 2  1135 laurel             0.800 gramm
 5  1256 spaghetti rinf   375.000 gramm
 2  1130 corned beef       80.000 gramm
 3  1139 mustard           15.000 gramm
 2  1136 clove              2.000 gramm

Answer 1

Try to put subquery in from, so that is easier to you to group columns without conditionally selecting two values:

SELECT sum(temp.used_times), temp.code, temp.f_name, sum(temp.qty), max(temp.meas)
FROM (SELECT f.qtyu AS used_times,
             COALESCE(i.ingr_code, f.food_code) AS code,
             COALESCE(i.ingr_name, f.food_name) AS f_name,
             (COALESCE(i.qtyi, 1) * f.qtyu)::decimal(11,3) AS qty,
             COALESCE(i.meas, f.meas) AS meas
      FROM usedfood f LEFT JOIN ingredients i
      ON f.food_code = i.food_code) as temp
GROUP BY temp.code, temp.f_name
ORDER BY temp.code

Answer 2

Are you looking for this?

SELECT SUM(f.qtyu) AS used_times,
       COALESCE(i.ingr_code, f.food_code) AS code,
       COALESCE(i.ingr_name, f.food_name) AS f_name,
       SUM(COALESCE(i.qtyi, 1) * f.qtyu)::decimal(11,3) AS qty,
       COALESCE(i.meas, f.meas) AS meas
  FROM usedfood f LEFT JOIN ingredients i
    ON f.food_code = i.food_code
 GROUP BY COALESCE(i.ingr_code, f.food_code), 
          COALESCE(i.ingr_name, f.food_name),
          COALESCE(i.meas, f.meas)
 ORDER BY code;

Output:

| USED_TIMES | CODE |           F_NAME | QTY |  MEAS |
|------------|------|------------------|-----|-------|
|          2 |  173 |          ketchup |   2 |   pcs |
|          2 |  175 | worchester sauce |   2 |   pcs |
|          1 |  177 |         parmesan |   1 |   pcs |
|          2 | 1130 |      corned beef |  80 | gramm |
|          2 | 1135 |           laurel | 0.8 | gramm |
|          2 | 1136 |            clove |   2 | gramm |
|          2 | 1138 |           tomato | 160 | gramm |
|          3 | 1139 |          mustard |  15 | gramm |
|          3 | 1140 |        fresh egg | 150 | gramm |
|          8 | 1144 |             salt | 3.4 | gramm |
|          5 | 1256 |   spaghetti rinf | 375 | gramm |
|          8 | 1258 |              oil | 362 | gramm |

Here is SQLFiddle demo