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card和ec_products是一个数据库(card)的两张表,
card_kind是另一个数据库(card_kind)的表
在card库中查询语句如下:
SELECT
card.id,
card.card_num AS cardNum,
ec_products.name,
card_kind.card_kind.cardKindType,
card_kind.card_kind.amount
FROM
card
LEFT JOIN
ec_products
ON
card.id = ec_products.card_id
LEFT JOIN
card_kind.card_kind
ON
ec_products.card_kind_id=card_kind.card_kind.id
关键句:
LEFT JOIN
card_kind.card_kind
ON
ec_products.card_kind_id=card_kind.card_kind.id