Mysql d：聚合和删除重复项的过程相当慢。必须先订购所有数据才能完成此操作。对于大型表，这可能是一项相当艰巨的任务。（对于小表，这不会有太大区别。）无论如何：只有在遇到性能问题时，才考虑加快查询速度。不要混淆查询，因为您认为这可能会以某种方式欺骗DBMS生成更好的
Mysql d：聚合和删除重复项的过程相当慢。必须先订购所有数据才能完成此操作。对于大型表，这可能是一项相当艰巨的任务。（对于小表，这不会有太大区别。）无论如何：只有在遇到性能问题时，才考虑加快查询速度。不要混淆查询，因为您认为这可能会以某种方式欺骗DBMS生成更好的,mysql,sql,database,group-by,distinct,Mysql,Sql,Database,Group By,Distinct,d：聚合和删除重复项的过程相当慢。必须先订购所有数据才能完成此操作。对于大型表，这可能是一项相当艰巨的任务。（对于小表，这不会有太大区别。）无论如何：只有在遇到性能问题时，才考虑加快查询速度。不要混淆查询，因为您认为这可能会以某种方式欺骗DBMS生成更好的执行计划。 SELECT CD.id AS id, CD.commodity_name_en AS commodity_name_en FROM MarketDetails AS MD INNE
d：聚合和删除重复项的过程相当慢。必须先订购所有数据才能完成此操作。对于大型表，这可能是一项相当艰巨的任务。（对于小表，这不会有太大区别。）无论如何：只有在遇到性能问题时，才考虑加快查询速度。不要混淆查询，因为您认为这可能会以某种方式欺骗DBMS生成更好的执行计划。
SELECT
CD.id AS id,
CD.commodity_name_en AS commodity_name_en
FROM MarketDetails AS MD
INNER JOIN MarketDetails_CommodityDetails AS MD_CD
ON MD.id = MD_CD.market_details_id
INNER JOIN CommodityDetails AS CD
on MD_CD.commodity_details_id = CD.id
WHERE MD.localization_id = 1
id commodity_name_en
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 Rice-Asia
2 Apple banana
3 Avocado
4 Red onion
5 White onion
6 Green Beans
7 Bell pepper
8 Carrot
9 Tomatoes
10 Irish potatoes
11 Maize
1 Rice-Asia
3 Avocado
5 White onion
8 Carrot
11 Maize
2 Apple banana
7 Bell pepper
9 Tomatoes
10 Irish potatoes
1 Rice-Asia
SELECT
CD.id AS id,
CD.commodity_name_en AS commodity_name_en
FROM MarketDetails AS MD
INNER JOIN MarketDetails_CommodityDetails AS MD_CD
ON MD.id = MD_CD.market_details_id
INNER JOIN CommodityDetails AS CD
on MD_CD.commodity_details_id = CD.id
WHERE MD.localization_id = 1
GROUP BY id
SELECT DISTINCT
CD.id AS id,
CD.commodity_name_en AS commodity_name_en
FROM MarketDetails AS MD
INNER JOIN MarketDetails_CommodityDetails AS MD_CD
ON MD.id = MD_CD.market_details_id
INNER JOIN CommodityDetails AS CD
on MD_CD.commodity_details_id = CD.id
WHERE MD.localization_id = 1
SELECT CD.id, CD.commodity_name_en
FROM CommodityDetails CD
WHERE EXISTS (SELECT 1
FROM MarketDetails MD INNER JOIN
MarketDetails_CommodityDetails MD_CD
ON MD.id = MD_CD.market_details_id
WHERE MD_CD.commodity_details_id = CD.id AND
MD.localization_id = 1
);
select id, commodity_name_en
from commoditydetails
where id in
(
select md_cd.commodity_details_id
from marketdetails_commoditydetails md_cd
join marketdetails md on md.id = md_cd.market_details_id
where md.localization_id = 1
);
select id, commodity_name_en
from commoditydetails
where id in
(
select commodity_details_id
from marketdetails_commoditydetails
where market_details_id in (select id from marketdetails where md.localization_id = 1)
);