PostgreSQL的，語法查詢問題

Question

我已經在我的問題得到很好的答案here

所以如果我創建表：

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'); 

，並從我的PostgreSQL執行這個查詢：

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 

...我仍然不能得到像這樣的預期結果SQL fiddle

我得到這樣的錯誤：

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...

這是最有可能的，這個代碼是不是在PostgreSQL完全兼容，所以請，如果有人可以從查詢解決這個代碼是正確的從PostgreSQL的系統運行。

Answer 1

這些問題主要是由於PostgreSQL（與大多數其他RDBMS類似，但與MySQL不同）需要將選定項目分組或彙總到分組/聚合查詢中。請嘗試：

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。