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我遇到了一个问题，我不知道为什么会给我带来麻烦。

我想使用 DISTINCT 语句从数据库中选择所有报价，因此每个报价 ID 都是唯一的。这是我在 Navicat 上以屏幕截图形式获得的内容：

截图 http://www.dreshar.com/sql.jpg http://www.dreshar.com/sql.jpg

对于看不到图像的任何人，这是选择 - 我的错误在哪里？

SELECT DISTINCT
guf_offers.id as OfferId,
guf_offers.validfrom AS OfferValidFrom,
guf_offers.validtill AS OfferValidTill,
guf_offers.days AS OfferDays,
guf_offers.active,
guf_offers.roomtype1 AS OfferRoomtype1,
guf_offers.roomprice1 AS OfferRoomprice1,
guf_countries.caption AS CountryCaption,
guf_courts.caption AS CourtCaption,
guf_hotels.caption AS HotelCaption,
guf_hotels.id AS HotelId,
guf_hotel_images.image AS HotelImage,
guf_offer_types.caption AS OffertypeCaption,
guf_regions.caption AS RegionCaption,
guf_offers.hoteloncourse AS OfferHotelOnCourse,
guf_offers.wellnessspa AS OfferWellnessSpa,
guf_offers.18hole AS Offer18Hole,
guf_offers.topangebot AS OfferTopangebot
FROM guf_offers , guf_countries , guf_courts , guf_hotels , guf_hotel_images , guf_offer_types , guf_regions
WHERE guf_offers.country_id = guf_countries.id AND guf_offers.court_id = guf_courts.id AND guf_offers.hotel_id = guf_hotels.id AND guf_hotel_images.hotel_id = guf_offers.hotel_id AND guf_offers.offer_type_id = guf_offer_types.id AND guf_offers.region_id = guf_regions.id AND guf_offers.active = 1 AND STR_TO_DATE(guf_offers.validtill, '%d.%m.%Y') > STR_TO_DATE('29.04.2013', '%d.%m.%Y')
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2 回答 2

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DISTINCT 返回任何不同的列组合。例如，图像中 OfferId = 89 的前两个实例在 HotelImage 列中显示不同的值，因此这些是 DISTINCT 结果。

于 2013-04-29T16:49:07.033 回答
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如果您想要不同的 id，那么您可能想要使用group by. 查询看起来像：

SELECT
guf_offers.id as OfferId,
guf_offers.validfrom AS OfferValidFrom,
guf_offers.validtill AS OfferValidTill,
guf_offers.days AS OfferDays,
guf_offers.active,
guf_offers.roomtype1 AS OfferRoomtype1,
guf_offers.roomprice1 AS OfferRoomprice1,
guf_countries.caption AS CountryCaption,
guf_courts.caption AS CourtCaption,
guf_hotels.caption AS HotelCaption,
guf_hotels.id AS HotelId,
guf_hotel_images.image AS HotelImage,
guf_offer_types.caption AS OffertypeCaption,
guf_regions.caption AS RegionCaption,
guf_offers.hoteloncourse AS OfferHotelOnCourse,
guf_offers.wellnessspa AS OfferWellnessSpa,
guf_offers.18hole AS Offer18Hole,
guf_offers.topangebot AS OfferTopangebot
FROM guf_offers , guf_countries , guf_courts , guf_hotels , guf_hotel_images , guf_offer_types , guf_regions
WHERE guf_offers.country_id = guf_countries.id AND guf_offers.court_id = guf_courts.id AND guf_offers.hotel_id = guf_hotels.id AND guf_hotel_images.hotel_id = guf_offers.hotel_id AND guf_offers.offer_type_id = guf_offer_types.id AND guf_offers.region_id = guf_regions.id AND guf_offers.active = 1 AND STR_TO_DATE(guf_offers.validtill, '%d.%m.%Y') > STR_TO_DATE('29.04.2013', '%d.%m.%Y')
group by guf_offers.id

其他列是来自不同行的任意值。group by这使用了对where 列的扩展，select即使它们不在聚合函数或group by子句中。

顺便说一句，您应该学习使用正确的语法在from子句中进行连接。join它使查询更具可读性和可维护性。

于 2013-04-29T17:56:23.447 回答