如何粉碎XML？

Question

如果我有一个像这样定义的SQL Server表：

CREATE TABLE MyData
(
     StepDescription VARCHAR(500), 
     StepDatetime DATETIME, 
     Filedata XML
)

在一条记录中，Filedata是：

<DocumentElement>
    <Data>
        <Security>BBG008LF20Q4</Security>
        <IsValidSecurityID>Y</IsValidSecurityID>
        <PX_LAST>101.073000</PX_LAST>
        <LAST_UPDATE_DT>2017/09/01</LAST_UPDATE_DT>
        <CRNCY>USD</CRNCY>
        <YellowKey>Corp</YellowKey>
        <YellowKeySpecified>true</YellowKeySpecified>
        <GenevaID>00206RCM2</GenevaID>
        <InvestmentCurrency>USD</InvestmentCurrency>
    </Data>
    <Data>
        <Security>BBG0050NM379</Security>
        <IsValidSecurityID>Y</IsValidSecurityID>
        <PX_LAST>103.405000</PX_LAST>
        <LAST_UPDATE_DT>2017/09/01</LAST_UPDATE_DT>
        <CRNCY>USD</CRNCY>
        <YellowKey>Corp</YellowKey>
        <YellowKeySpecified>true</YellowKeySpecified>
        <GenevaID>257867AZ4</GenevaID>
        <InvestmentCurrency>USD</InvestmentCurrency>
    </Data>
</DocumentElement>   

在记录2中，Filedata是：

<DocumenElement>
    <Data>
        <Security>86765LAC1</Security>
        <IsValidSecurityID>Y</IsValidSecurityID>
        <MARKET_SECTOR_DES>Corp</MARKET_SECTOR_DES>
        <SECURITY_TYP>GLOBAL</SECURITY_TYP>
        <CRNCY>USD</CRNCY>
        <ID_BB_GLOBAL>BBG00DR79B93</ID_BB_GLOBAL>
        <ID_BB_UNIQUE>COQZ4428111</ID_BB_UNIQUE>
        <ID_CUSIP>86765LAC1</ID_CUSIP>
        <ID_ISIN>US86765LAC19</ID_ISIN>
        <TICKER>SUN</TICKER>
        <EXCH_CODE>NEW YORK</EXCH_CODE>
        <PARSEKYABLE_DES>QZ442811     Corp</PARSEKYABLE_DES>
        <NAME>SUNOCO LP/FINANCE CORP</NAME>
        <ID_BB_SEC_NUM_DES>SUN 5.5 08/01/20</ID_BB_SEC_NUM_DES>
        <ID_BB_ULTIMATE_PARENT_CO_NAME>Sunoco LP</ID_BB_ULTIMATE_PARENT_CO_NAME>
        <ID_MIC1>XNYS</ID_MIC1>
        <CPN_CRNCY>USD</CPN_CRNCY>
        <LONG_COMP_NAME>Sunoco LP / Sunoco Finance Corp</LONG_COMP_NAME>
        <ADJUSTABLE>N</ADJUSTABLE>
        <CPN_TYP>FIXED</CPN_TYP>
        <CNTRY_ISSUE_ISO>US</CNTRY_ISSUE_ISO>
        <COUNTRY>US</COUNTRY>
        <IS_QDI_ELIGIBLE>No</IS_QDI_ELIGIBLE>
        <_x0020_EXCH_CODE>NEW YORK</_x0020_EXCH_CODE>
        <WHEN_ISSUED>N</WHEN_ISSUED>
        <DAY_CNT_DES>30/360</DAY_CNT_DES>
        <CPN>5.500000</CPN>
        <CPN_FREQ>2</CPN_FREQ>
        <INT_ACC_DT>2016/08/01</INT_ACC_DT>
        <ISSUE_DT>2016/10/03</ISSUE_DT>
        <FIRST_CPN_DT>2017/02/01</FIRST_CPN_DT>
        <FIRST_CPN_PERIOD_TYP>Normal</FIRST_CPN_PERIOD_TYP>
        <MATURITY>2020/08/01</MATURITY>
        <MTY_TYP>CALLABLE</MTY_TYP>
        <REDEMP_VAL>100.00000</REDEMP_VAL>
        <PENULTIMATE_CPN_DT>2020/02/01</PENULTIMATE_CPN_DT>
        <SINKABLE>N</SINKABLE>
        <CUR_MKT_CAP>3130.29</CUR_MKT_CAP>
        <PX_LAST>103.162000</PX_LAST>
        <DAYS_TO_SETTLE>2</DAYS_TO_SETTLE>
        <PAY_IN_KIND_BONDS>N</PAY_IN_KIND_BONDS>
        <US_SECTION_13F_SECURITY>N</US_SECTION_13F_SECURITY>
        <RTG_MOODY>B1</RTG_MOODY>
        <RTG_SP>B+</RTG_SP>
        <RTG_FITCH>BB- /*+</RTG_FITCH>
        <CNTRY_OF_RISK>US</CNTRY_OF_RISK>
        <_x0031_44A_FLAG>N</_x0031_44A_FLAG>
        <IS_REG_S>N</IS_REG_S>
        <CNTRY_OF_DOMICILE>US</CNTRY_OF_DOMICILE>
        <IS_EMERGING_MARKET>N</IS_EMERGING_MARKET>
        <YellowKey>Corp</YellowKey>
        <YellowKeySpecified>true</YellowKeySpecified>
    </Data>
</DocumentElement>

现在我需要创建如下的行：

StepDescription, StepDatetime, FieldName, FieldValue

所以对于第一张唱片，我会：

Step1, 10/31/2017, Security, IsValidSecurityID
Step1, 10/31/2017, Security, PX_LAST
Step1, 10/31/2017, Security, LAST_UPDATE_DT

基本上，我试图在不事先知道节点的情况下粉碎XML。

我如何在SQL Server中实现这一目标？

感谢。