对本机函数'ISNULL‘的调用中的参数计数错误

Question

我有一个查询，我正试图从MS SQL Server2008转换为MySQL。它在MSSQL上运行得很好，我得到了错误"Incorrect parameter count in the call to native function 'ISNULL'“。

我该如何解决这个问题？

SELECT DISTINCT
    dbo.`@EIM_PROCESS_DATA`.U_Tax_year,
    dbo.`@EIM_PROCESS_DATA`.U_Employee_ID,
    CASE
        WHEN dbo.`@EIM_PROCESS_DATA`.U_PD_code = 'SYS033' THEN SUM(dbo.`@EIM_PROCESS_DATA`.U_Amount)
    END AS PAYE,
    CASE
        WHEN dbo.`@EIM_PROCESS_DATA`.U_PD_code = 'SYS014' THEN SUM(dbo.`@EIM_PROCESS_DATA`.U_Amount)
    END AS TOTALTAXABLE,
    dbo.OADM.CompnyName,
    dbo.OADM.CompnyAddr,
    dbo.OADM.TaxIdNum,
    dbo.OHEM.lastName + ', ' + ISNULL(dbo.OHEM.middleName, '') + '' + ISNULL(dbo.OHEM.firstName, '') AS EmployeeName
FROM
    dbo.`@EIM_PROCESS_DATA`
        INNER JOIN
    dbo.OHEM ON dbo.`@EIM_PROCESS_DATA`.U_Employee_ID = dbo.OHEM.empID
        CROSS JOIN
    dbo.OADM
GROUP BY dbo.`@EIM_PROCESS_DATA`.U_Tax_year , dbo.`@EIM_PROCESS_DATA`.U_Employee_ID , dbo.OADM.CompnyName , dbo.OADM.CompnyAddr , dbo.OADM.TaxIdNum , dbo.OHEM.lastName , dbo.OHEM.firstName , dbo.OHEM.middleName , dbo.`@EIM_PROCESS_DATA`.U_PD_code

MySQL

SELECT DISTINCT 
     processdata.taxYear, processdata.empID, 
     CASE WHEN processdata.edCode = 'SYS033' THEN SUM (processdata.amount) END AS PAYE, 
     CASE WHEN processdata.edCode = 'SYS014' THEN SUM (processdata.amount) END AS TOTALTAXABLE, 
     company.companyName, company.streetAddress, company.companyPIN, employeemaster.lastName + ', ' + IFNULL(employeemaster.middleName, '') 
     + ' ' + IFNULL(employeemaster.firstName, '') AS EmployeeName
FROM         
     processdata INNER JOIN
     employeemaster ON processdata.empID = employeemaster.empID 
     CROSS JOIN company
     GROUP BY processdata.taxYear, processdata.empID, company.companyName, company.streetAddress, company.companyPIN, 
     employeemaster.lastName, employeemaster.firstName, employeemaster.middleName, processdata.edCode

Answer 1

ISNULL在MySQL中的等价物是IFNULL

如果expr1不为空，则

()返回expr1；否则返回expr2。

也许还可以看看SQL NULL Functions

The ISNULL from MySQL is used to check if a value is null

如果

为NULL，则ISNULL()返回1，否则返回0。

Answer 2

我建议您切换到ANSI标准函数coalesce()

(dbo.OHEM.lastName + ', ' + coalesce(dbo.OHEM.middleName, '') + '' + coalesce(dbo.OHEM.firstName, '')
) AS EmployeeName

您还可以通过包含表别名来使查询更易于阅读。

编辑：

需要注意的是，我似乎错过了转换的方向。MySQL查询将使用concat()

CONCAT(OHEM.lastName, ', ', coalesce(OHEM.middleName, ''),
       coalesce(concat(' ', OHEM.firstName), '')
      ) AS EmployeeName

Answer 3

在对包含ISNULL(value)的查询运行JUnit测试时，我得到了一个错误，错误是ISNULL需要两个参数。我通过更改查询以使value is null和代码工作相同来修复此问题，同时测试现在也可以工作。