public virtual async Task Functions_CountDistinct()
{
using (var tempTable = await DataTestHelpers.CreateAutoIncrementTable(DataProvider))
{
await DataProvider.ExecuteNonQueryAsync(QueryExpression.Insert(
tempTable.TableName,
new[] { "Data" },
new object[] { 10 },
new object[] { 10 },
new object[] { 15 },
new object[] { 20 }
));
using (var queryResult = await DataProvider.ExecuteReaderAsync(
QueryExpression.Select(
new[] { QueryExpression.CountFunction(
QueryExpression.Distinct(QueryExpression.Column("Data"))
) },
from: QueryExpression.Table(tempTable.TableName)
)))
{
Assert.IsTrue(queryResult.HasRows);
Assert.IsTrue(await queryResult.ReadAsync());
Assert.AreEqual(3, queryResult.GetInt32(0));
}
}
}
public ExpressionResult Convert(MethodInfo methodInfo, MethodCallExpression node,
ExpressionConverter expressionConverter)
{
var expressionResult = expressionConverter.Convert(node.Arguments[0]);
var countExpression = expressionResult.QueryExpression;
if (countExpression is TableExpression)
{
countExpression = QueryExpression.All();
}
return(new ExpressionResult(
QueryExpression.CountFunction(countExpression),
expressionResult.RequiredJoins
));
}
public virtual async Task Functions_Count()
{
// some database engines require the subquery to be aliased
using (var tempTable = await Select_CreatePopulatedSelectTable())
{
using (var queryResult = await DataProvider.ExecuteReaderAsync(
QueryExpression.Select(
new[] { QueryExpression.CountFunction(QueryExpression.All()) },
from: QueryExpression.Table(tempTable.TableName)
)))
{
Assert.IsTrue(queryResult.HasRows);
Assert.IsTrue(queryResult.Read());
Assert.AreEqual(6, queryResult.GetInt32(0));
}
}
}