/// <inheritdoc/>
protected override SqlProvider VisitExistence(ExistenceProvider provider)
{
var source = Compile(provider.Source);
var query = source.Request.Statement.ShallowClone();
query.Columns.Clear();
query.Columns.Add(query.Asterisk);
query.OrderBy.Clear();
query.GroupBy.Clear();
SqlExpression existsExpression = SqlDml.Exists(query);
existsExpression = GetBooleanColumnExpression(existsExpression);
var select = SqlDml.Select();
select.Columns.Add(existsExpression, provider.ExistenceColumnName);
return(CreateProvider(select, provider, source));
}
/// <summary> /// Compiles <see cref="ExistenceProvider"/>. /// </summary> /// <param name="provider">Existence provider.</param> protected abstract TResult VisitExistence(ExistenceProvider provider);
