???????????????????????嵥1?????
????1: SELECT    *
????2: FROM      HumanResources.Employee
????3: WHERE     NationalIDNumber = 243322160
????4:
????5: SELECT    *
????6: FROM      HumanResources.Employee
????7: WHERE     NationalIDNumber = '243322160'
?????????嵥1.
????NationalIDNumber?ж?????Nvarchar??????????????INT???????????Varchar???????????????????????????????????????????????https://msdn.microsoft.com/zh-cn/library/ms190309.aspx????????????????Nvarchar??INT?????????INT???????????????????????NationalIDNumber????INT?????????漰??????????и????????INT??????????????????????????????
???????????嵥1?е?????????NationalIDNumber???Nvarchar????????????varchar?????????????????????????????Varchar????Navrchar????????????????????????????????????????
????????????????????????????????
??????SQL Server?У???м???????????????????????и??á?SQL Server????????DMV???????Щ??м??????????м?????????XML????????XQUERY??????????м??????????
????????м???У?????????????????????????????嵥2???????Σ?
????1: <Convert DataType="int" Style="0" Implicit="true">
????2:                                   <ScalarOperator>
????3:                                     <Identifier>
????4:                                       <ColumnReference Database="[AdventureWorks2012]" Schema="[HumanResources]" Table="[Employee]" Column="NationalIDNumber" />
????5:                                     </Identifier>
????6:                                   </ScalarOperator>
????7:                                 </Convert>
?????????嵥2.???н??????????м?????
?????????????ж??ж????????????????????????????????????????嵥2?ж??н?????????????м???????t???????????????????????????????????????????????????????????????ò???????????嵥3?????
????1: <Convert DataType="nvarchar" Length="8000" Style="0" Implicit="true">
????2:                                     <ScalarOperator>
????3:                                       <Identifier>
????4:                                         <ColumnReference Column="@1" />
????5:                                       </Identifier>
????6:                                     </ScalarOperator>
????7:                                   </Convert>