我正在为 MySQL 查询而苦苦挣扎。这是问题所在:
SELECT * from sf_forecasts WHERE contentid='1234' AND fulldate='2012-12-13'
我的表中有一条记录符合这个条件,这个查询很容易找到它。但是,当我使用此查询进行更新时...
UPDATE sf_forecasts
SET listingTitle ='Some Snow Resort', location ='49.23, -115.22'
WHERE contentid='1234' AND fulldate='2012-12-13'
...我总是收到“0 行受影响”的通知。奇怪的是,查询实际上是在更新记录,但它只是触及 NULL 字段。如果我的示例记录的“位置”值为 NULL,则查询将更新数据,但如果它已经包含非 NULL 值,则查询不会更改它,即使查询清楚地包含新信息。
是什么赋予了?
PS如果这很重要,我正在使用contentid + fulldate(b-tree,唯一)的PRIMARY键。
PSS 下面是“SHOW CREATE TABLE sf_forecasts”的结果,要求如下:
sf_forecasts CREATE TABLE `sf_forecasts` (
`contentid` int(11) NOT NULL,
`fulldate` varchar(10) COLLATE utf8_unicode_ci NOT NULL,
`listingTitle` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`location` varchar(10) COLLATE utf8_unicode_ci NOT NULL,
`dayofmonth` smallint(2) NOT NULL,
`dayofweek` varchar(10) COLLATE utf8_unicode_ci NOT NULL,
`minTempF` smallint(4) NOT NULL,
`maxTempF` smallint(4) NOT NULL,
`minTempC` smallint(4) NOT NULL,
`maxTempC` smallint(4) NOT NULL,
`skyCondition` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`precip` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`snowPotential` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`wind` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`minTempF_custom` smallint(4) DEFAULT NULL,
`maxTempF_custom` smallint(4) DEFAULT NULL,
`minTempC_custom` smallint(4) DEFAULT NULL,
`maxTempC_custom` smallint(4) DEFAULT NULL,
`baseH_custom` smallint(4) DEFAULT NULL,
`baseL_custom` smallint(4) DEFAULT NULL,
`topH_custom` smallint(4) DEFAULT NULL,
`topL_custom` smallint(4) DEFAULT NULL,
`skyCondition_custom` varchar(200) COLLATE utf8_unicode_ci DEFAULT NULL,
`precip_custom` varchar(200) COLLATE utf8_unicode_ci DEFAULT NULL,
`snowPotential_custom` varchar(200) COLLATE utf8_unicode_ci DEFAULT NULL,
`wind_custom` varchar(200) COLLATE utf8_unicode_ci DEFAULT NULL,
`icon` varchar(30) COLLATE utf8_unicode_ci NOT NULL,
`icon_custom` varchar(30) COLLATE utf8_unicode_ci DEFAULT NULL,
`shortrange_custom` varchar(5000) COLLATE utf8_unicode_ci DEFAULT NULL,
`longrange_custom` varchar(5000) COLLATE utf8_unicode_ci DEFAULT NULL,
`scCode` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`scUpdate` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`lastUpdate` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`skys` varchar(30) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`contentid`,`fulldate`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci