mysql - 使用 SUM 和 JOIN 获取唯一值

Question

我正在尝试获取 calc.transport 的总数表 3_product_folder 包含重复值(列“folder_id”)，如何防止弄乱 SUM？我尝试过 DISTINCT 但没有成功。

有什么建议吗？

SELECT
SUM(calc.transport) AS transport
FROM 0_calculatie_id AS calc
LEFT JOIN 0_calculatie_inh_id AS id
ON id.calculatie_id = calc.id
LEFT JOIN 3_product_folder AS fld_id
ON fld_id.product_id = id.id
LEFT JOIN 4_folder_dossier AS fld
ON fld.product_folder_id = fld_id.folder_id
LEFT JOIN 10_factuur_inh AS fac_inh
ON fac_inh.folder_id = fld.id
LEFT JOIN 9_factuur_id AS fac
ON fac.id = fac_inh.factuur_id
WHERE YEAR(fac.datum_verstuurd) = ".$row['jaar']." AND MONTH(fac.datum_verstuurd) = ".$row_mth2['maand']."

我尝试过这个嵌套查询，但并非所有项目都会被计算:

SELECT
SUM(temp.transport) AS transport
FROM
(SELECT DISTINCT
calc.transport,
fld_id.folder_id
FROM 0_calculatie_id AS calc
LEFT JOIN 0_calculatie_inh_id AS id
ON id.calculatie_id = calc.id
LEFT JOIN 3_product_folder AS fld_id
ON fld_id.product_id = id.id
LEFT JOIN 4_folder_dossier AS fld
ON fld.product_folder_id = fld_id.folder_id
LEFT JOIN 10_factuur_inh AS fac_inh
ON fac_inh.folder_id = fld.id
LEFT JOIN 9_factuur_id AS fac
ON fac.id = fac_inh.factuur_id
WHERE YEAR(fac.datum_verstuurd) = 2012 AND MONTH(fac.datum_verstuurd) = 7) AS temp

Answer 1

表的结构是什么？

您尚未对 SQL 语句进行分组:

WHERE YEAR(fac.datum_verstuurd) = ".$row['jaar']." AND MONTH(fac.datum_verstuurd) = ".$row_mth2['maand']."
GROUP BY fld_id.product_id