Question

我在变量中声明了一个select查询。现在我想检查查询是否返回0行，然后我必须使用其他条件。我正在使用SQL SERVER 2012.如果变量包含0行，如何检查变量。请建议

  set @sql = 'select tsf.StaffId,tsf.FullName,tsf.[Address],tsf.PhoneNo,tsf.Email,tsf.Gender,tsf.MobileNo1,tsf.MobileNo2, tsf.Post,                         tsf.Salary,ts.AdvanceSalary,ts.[Description],ts.[Month] from Tbl_Salary ts
                        JOIN Tbl_Staff tsf on ts.StaffId = tsf.StaffId'
                        If @CategoryId is not null        
                        set @sql = @sql + ' where tsf.StaffId='''+cast(@CategoryId as varchar(10))+''''
                        If @MonthName is not null
                        set @sql = @sql +' and ts.Month='''+cast(@MonthName as varchar(50))+''''
                        If @Year is not null
                        set @sql = @sql +' and ts.Year='''+cast(@Year as varchar(50))+''''
            exec(@sql)

Answer 1

您只需将查询更改为

即可

select COUNT(*)
from Tbl_Machine where MachineId = @MachineId

如果您只对计数感兴趣，则无需传输所有这些数据行。

此外，几乎所有数据库库在执行查询时都会返回一个包含行数的属性 - 您可能希望查看您正在使用的任何库。

查看您的更新，这里绝对不需要动态SQL - 使用它会破坏您的性能。你只需要一些条件逻辑

select tsf.StaffId,tsf.FullName,tsf.   [Address],tsf.PhoneNo,tsf.Email,tsf.Gender,tsf.MobileNo1,tsf.MobileNo2, tsf.Post,                         tsf.Salary,ts.AdvanceSalary,ts.[Description],ts.[Month] 
from Tbl_Salary ts
JOIN Tbl_Staff tsf on ts.StaffId = tsf.StaffId
WHERE (@CategoryId IS NULL OR tsf.StaffId=@CategoryID)
AND (@MonthName IS NULL OR ts.Month=@MonthName)
AND (@Year IS NULL OR and ts.Year=@Year)

Answer 2

您还应该检查@@rowcount，

返回受最后一个语句影响的行数。

因此，在您的查询后添加

  IF @@ROWCOUNT =0
  BEGIN
  --do something
  END

请务必阅读@@ROWCOUNT (Transact-SQL)

Answer 3

if not exists
(select MachineId, MachineName, PurchasedDate, CompanyName, ModelNo, Amount, InsuranceCom,
 MnthlyInstallAmt, TotalPaid, MnthlyInstallDate from Tbl_Machine 
 where MachineId = @MachineId)
begin
--returned 0 rows
--go with other conditions
end

Answer 4

set @sql = "select count(temp_all.MachineId) AS 'Total_count' from 
           (select MachineId, MachineName, PurchasedDate, CompanyName,  ModelNo, 
            Amount, InsuranceCom, MnthlyInstallAmt, TotalPaid, MnthlyInstallDate
            from Tbl_Machine where MachineId = @MachineId) AS temp_all"

如何计算SQL Server中所选行的返回值？

4 个答案: