EF core Get Count and sum in one call-CodePudding

Using Entity Framework core, can I get the total sum of the column and row count in one call? I have the following code, but I think there is a better way to do this.

TotalCostResponse result = new TotalCostResponse
{
    TotalCost = await dbContext.Transaction
        .Where(x => x.UserName == request.UserName
            && x.Date >= request.StartDate
            && x.Date <= request.EndDate)
        .SumAsync(x => x.Amount),

    TotalNumber = await dbContext.Transaction
        .Where(x => x.UserName == request.UserName
            && x.Date = request.StartDate
            && x.Date <= request.EndDate)
        .CountAsync()
};

So instead of calling dbContext two times, I need to make it in one call.

CodePudding user response：

var result = await dbContext.Transaction
    .Where(x => x.UserName == request.UserName
        && x.Date >= request.StartDate
        && x.Date <= request.EndDate)
    .GroupBy(x => 1)
    .Select(group => new TotalCostResponse
    {
        TotalCost = group.Sum(x => x.Amount),
        TotalNumber = group.Count()
    })
    .FirstOrDefaultAsync();

CodePudding user response：

Yes, you can get the total sum and row count in a single call to the database using the Sum and Count methods together in a LINQ query. Here is an example of how you could do this:

TotalCostResponse result = new TotalCostResponse
{
// Use the Sum and Count methods together in a LINQ query to get the total sum
// and row count in a single call to the database.
TotalCost = await dbContext.Transaction
    .Where(x => x.UserName == request.UserName
        && x.Date >= request.StartDate
        && x.Date <= request.EndDate)
    .Select(x => new
    {
        // Select the Amount column and use the Sum method to get the total sum.
        TotalCost = x.Amount.Sum(),
        // Use the Count method to get the row count.
        TotalNumber = x.Amount.Count()
    })
    // Use the SingleOrDefault method to get the first element of the query result.
    // If the query result is empty, this will return null.
    .SingleOrDefault(),

// If the query result is not null, set the TotalCost and TotalNumber properties
// of the TotalCostResponse object using the values from the query result.
// If the query result is null, these properties will remain uninitialized.
TotalCost = result?.TotalCost,
TotalNumber = result?.TotalNumber
};

Alternatively, you could use the Sum and Count methods in separate LINQ queries and then combine the results in memory, like this:

// Use the Sum method in a LINQ query to get the total sum.
decimal? totalCost = await dbContext.Transaction
.Where(x => x.UserName == request.UserName
    && x.Date >= request.StartDate
    && x.Date <= request.EndDate)
.SumAsync(x => x.Amount);

// Use the Count method in a LINQ query to get the row count.
int? totalNumber = await dbContext.Transaction
.Where(x => x.UserName == request.UserName
    && x.Date = request.StartDate
    && x.Date <= request.EndDate)
.CountAsync();

TotalCostResponse result = new TotalCostResponse
{
// Set the TotalCost and TotalNumber properties of the TotalCostResponse
// object using the values from the LINQ queries.
TotalCost = totalCost,
TotalNumber = totalNumber
};

Both of these approaches will allow you to get the total sum and row count in a single call to the database, which should be more efficient than making two separate calls like in your original code.

CodePudding user response：

Here is an example with one querry, There are certainly other ways tath you can find.

//In the select get only what you need, in your case only the Amount
var transactions = await this.dbContext.Transaction
               .Where(x => x.UserName == request.UserName
               && x.Date >= request.StartDate
               && x.Date <= request.EndDate)
               .Select(y => new
               {
                  Amount = y.Amount,
               }).ToListAsync();

//Calculating the data
var result = new TotalCostResponse
{
   TotalCost = transactions.Sum(x => x),
   TotalNumber = transactions.Count(),
}

//Dto model for the result
public class TotalCostResponse
{
   public decimal TotalCost { get; set; }
   public int TotalNumber { get; set; } 
}