MySQL主键列不是唯一的吗？

Question

I have the following table in a MySQL database:

CREATE TABLE `datavalues` (
  `ValueID` int(11) NOT NULL AUTO_INCREMENT,
  `DataValue` double NOT NULL,
  `ValueAccuracy` double DEFAULT NULL,
  `LocalDateTime` datetime NOT NULL,
  `UTCOffset` double NOT NULL,
  `DateTimeUTC` datetime NOT NULL,
  `SiteID` int(11) NOT NULL,
  `VariableID` int(11) NOT NULL,
  `OffsetValue` double DEFAULT NULL,
  `OffsetTypeID` int(11) DEFAULT NULL,
  `CensorCode` varchar(50) COLLATE utf8_unicode_ci NOT NULL DEFAULT 'nc',
  `QualifierID` int(11) DEFAULT NULL,
  `MethodID` int(11) NOT NULL DEFAULT '0',
  `SourceID` int(11) NOT NULL,
  `SampleID` int(11) DEFAULT NULL,
  `DerivedFromID` int(11) DEFAULT NULL,
  `QualityControlLevelID` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`ValueID`),
  UNIQUE KEY `DataValues_UNIQUE_DataValues`     (`DataValue`,`ValueAccuracy`,`LocalDateTime`,`UTCOffset`,`DateTimeUTC`,`SiteID`,`VariableID`,`OffsetValue`,`OffsetTypeID`,`CensorCode`,`QualifierID`,`MethodID`,`SourceID`,`SampleID`,`DerivedFromID`,`QualityControlLevelID`),
  KEY `FK_DataValues_Sites` (`SiteID`),
  KEY `FK_DataValues_Sources` (`SourceID`),
  KEY `FK_DataValues_QualityControlLevels` (`QualityControlLevelID`),
  KEY `FK_DataValues_OffsetTypes` (`OffsetTypeID`),
  KEY `FK_DataValues_CensorCodeCV` (`CensorCode`),
  KEY `FK_DataValues_Variables` (`VariableID`),
  KEY `FK_DataValues_Methods` (`MethodID`),
  KEY `FK_DataValues_Qualifiers` (`QualifierID`),
  KEY `FK_DataValues_Samples` (`SampleID`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

ALTER TABLE `datavalues`
  ADD CONSTRAINT `FK_DataValues_Sites` FOREIGN KEY (`SiteID`) REFERENCES `sites`     (`SiteID`) ON DELETE NO ACTION ON UPDATE CASCADE,
  ADD CONSTRAINT `FK_DataValues_Sources` FOREIGN KEY (`SourceID`) REFERENCES `sources` (`SourceID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_QualityControlLevels` FOREIGN KEY (`QualityControlLevelID`) REFERENCES `qualitycontrollevels` (`QualityControlLevelID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_OffsetTypes` FOREIGN KEY (`OffsetTypeID`) REFERENCES `offsettypes` (`OffsetTypeID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_CensorCodeCV` FOREIGN KEY (`CensorCode`) REFERENCES `censorcodecv` (`Term`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_Variables` FOREIGN KEY (`VariableID`) REFERENCES `variables` (`VariableID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_Methods` FOREIGN KEY (`MethodID`) REFERENCES `methods` (`MethodID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_Qualifiers` FOREIGN KEY (`QualifierID`) REFERENCES `qualifiers` (`QualifierID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `FK_DataValues_Samples` FOREIGN KEY (`SampleID`) REFERENCES `samples` (`SampleID`) ON DELETE NO ACTION ON UPDATE NO ACTION;

When I open my database in PhpMyAdmin 4.0.3 and run a query:

SELECT MAX(DateTimeUTC) from `datavalues` 

the query executes but PhpMyAdmin shows a warning:

This table does not contain a unique column. Grid edit, checkbox, Edit, Copy and Delete features are not available.

How is it possible? I thought that if I have one column with PRIMARY KEY constraint then the column is UNIQUE. Could this be a bug in PhpMyAdmin? I'm confused.

Answer 1

I found the answer: The warning:

This table does not contain a unique column. Grid edit, checkbox, Edit, Copy and Delete features are not available.

applies to the current result set and not to the original table. Álvaro G. Vicario's comment is right.

This appears to be a new thing in PhpMyAdmin 4.0.4 and I find this type of message more confusing than useful.

Answer 2

All you got to do is add a unique column like one called id with a index = PRIMARY like the pic, or if you have one already that is called id that are numbers just make it PRIMARY