PostgreSQL的，语法查询问题

Question

我已经在我的问题得到很好的答案here

所以如果我创建表：

CREATE TABLE IF NOT EXISTS usedfood 
(food_code int, name text, qty int, meas text); 

INSERT INTO usedfood (food_code, name, qty, meas) 
VALUES (10, 'spaghetti', 3, 'pcs'), 
     (156, 'mayonnaise', 2, 'pcs'), 
     (173, 'ketchup', 1, 'pcs'), 
     (172, 'bolognese sauce', 2, 'pcs'), 
     (173, 'ketchup', 1, 'pcs'), 
     (10, 'spaghetti', 2, 'pcs'), 
     (156, 'mayonnaise', 1, 'pcs'); 

CREATE TABLE IF NOT EXISTS ingredients 
(food_code int, ingr_code int, name text, qty decimal(11,3), meas text); 

INSERT INTO ingredients (food_code, ingr_code, name, qty, 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'); 

，并从我的PostgreSQL执行这个查询：

SELECT SUM(f.qty) used_times, 
COALESCE(i.ingr_code, f.food_code) code, 
COALESCE(i.name, f.name) name, 
SUM(COALESCE(i.qty, 1) * f.qty) qty, 
COALESCE(i.meas, f.meas) meas 
FROM usedfood f LEFT JOIN ingredients i 
ON f.food_code = i.food_code 
GROUP BY i.ingr_code, i.name 

...我仍然不能得到像这样的预期结果SQL fiddle

我得到这样的错误：

ERROR: syntax error at or near "name" LINE 1: ...code, f.food_code) code, COALESCE(i.name, f.name) name, SUM(...

ERROR: column "f.food_code" must appear in the GROUP BY clause or be used in an aggregate function LINE 1: ...LECT SUM(f.qty) used_times, COALESCE(i.ingr_code, f.food_cod...

ERROR: column "f.name" must appear in the GROUP BY clause or be used in an aggregate function LINE 1: ...(i.ingr_code, f.food_code) code, COALESCE(i.name, f.name) in...

ERROR: column "i.meas" must appear in the GROUP BY clause or be used in an aggregate function LINE 1: ...me, SUM(COALESCE(i.qty, 1) * f.qty) qty, COALESCE(i.meas, f....

ERROR: column "f.meas" must appear in the GROUP BY clause or be used in an aggregate function LINE 1: ...COALESCE(i.qty, 1) * f.qty) qty, COALESCE(i.meas, f.meas) me...

这是最有可能的，这个代码是不是在PostgreSQL完全兼容，所以请，如果有人可以从查询解决这个代码是正确的从PostgreSQL的系统运行。

Answer 1

这些问题主要是由于PostgreSQL（与大多数其他RDBMS类似，但与MySQL不同）需要将选定项目分组或汇总到分组/聚合查询中。请尝试：

SELECT SUM(f.qty) used_times, 
     COALESCE(i.ingr_code, max(f.food_code)) code, 
     COALESCE(i.name, max(f.name)) "name", 
     SUM(COALESCE(i.qty, 1) * f.qty) qty, 
     COALESCE(max(i.meas), max(f.meas)) meas 
    FROM usedfood f LEFT JOIN ingredients i 
    ON f.food_code = i.food_code 
GROUP BY i.ingr_code, i.name 

SQLFiddle here。