mysql - Many JOINs in a long SQL call -


there 4 tables, each tuple id(int),name(varchar) (the id autoincrementing). there table meal (cheeseburger, hamburger, meat feast, blt, tomato soup), class (burger, pizza, sandwich, soup), characteristics (spicy, vegtarian, gluten free), , sides(salad, fries, bread).

three more tables exist make tuples meal.id,class.id, meal.id,characteristics.id, meal.id,sides.id meal can in more 1 class, have more 1 characteristic, , come more 1 side, , vice versa.

i had following lazy loading fine, know that's not good. want name of meal, it's characteristics, sides , alternative meals same class.

this call worked fine:

select group_concat(distinct m2.meal_name separator ',')          alternates,        group_concat(distinct c.characteristic_desc separator ',')        characteristics   meal m        inner join mealclass mc                on m.meal_id = mc.meal_id        left join (select meal_id,                          class_id                     drugingredient) mc2               on mc2.class_id = mc.class_id        left join meals m2               on mc2.meal_id = m2.meal_id        left join mealchar mch               on mch.meal_id = m.meal_id        inner join characterisics c                on c.characteristic_id = mch.characteristic_id  m.meal_id = :meal_id        , m.meal_id <> m2.meal_id

but when extended out this, got nothing back:

select group_concat(distinct m2.meal_name separator ',')          alternates,        group_concat(distinct c.characteristic_desc separator ',')        characteristics,        group_concat(distinct s.sides_desc separator ',')          side_orders   meal m        inner join mealclass mc                on m.meal_id = mc.meal_id        left join (select meal_id,                          class_id                     drugingredient) mc2               on mc2.class_id = mc.class_id        left join meals m2               on mc2.meal_id = m2.meal_id        left join mealchar mch               on mch.meal_id = m.meal_id        inner join characterisics c                on c.characteristic_id = mch.characteristic_id        inner join mealsides ms                on m.meal_id = ms.meal_id        inner join sides s                on s.sides_id = ms.sides_id  m.meal_id = :meal_id        , m.meal_id <> m2.meal_id

any ideas how fix call, or how have better structured schema? or degree of lazy loading best way go here (:p)?!

there 3 possible things here. i've written them out demonstration.

create table (x integer, y integer); create table b (v integer, w integer); create table c (t integer, u integer); insert values (1,2); insert values (3,4); insert values (5,6); insert b values (1,2); insert b values (5,6); insert c values (1,2); insert c values (3,4);

this same used:
(a left join b) join c 

select * left join b on a.x = b.v join c on b.v = c.t;  x | y | v | w | t | u ---+---+---+---+---+---  1 | 2 | 1 | 2 | 1 | 2

this using left joins:
(a left join b) left join c 

select * left join b on a.x = b.v left join c on b.v = c.t;  x | y | v | w | t | u ---+---+---+---+---+---  1 | 2 | 1 | 2 | 1 | 2  3 | 4 |   |   |   |  5 | 6 | 5 | 6 |   |

i think aiming for: left join (b join c)

select * left join (b join c on b.v = c.t) on a.x = b.v;  x | y | v | w | t | u ---+---+---+---+---+---  1 | 2 | 1 | 2 | 1 | 2  3 | 4 |   |   |   |  5 | 6 |   |   |   |

hope helps


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