Added CountDistinct phrase

dg.Sql/Sql/Phrases/Quantitative/CountDistinct.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using dg.Sql.Connector;
+
+namespace dg.Sql.Phrases
+{
+    public class CountDistinct : IPhrase
+    {
+        string TableName;
+        object Object;
+        ValueObjectType ObjectType;
+
+        public CountDistinct(string tableName, string columnName)
+        {
+            this.TableName = tableName;
+            this.Object = columnName;
+            this.ObjectType = ValueObjectType.ColumnName;
+        }
+
+        public CountDistinct(string columnName)
+            : this(null, columnName)
+        {
+        }
+
+        public CountDistinct(object theObject, ValueObjectType objectType)
+        {
+            this.Object = theObject;
+            this.ObjectType = objectType;
+        }
+
+        public string BuildPhrase(ConnectorBase conn)
+        {
+            string ret;
+
+            ret = @"COUNT(DISTINCT ";
+
+            if (ObjectType == ValueObjectType.ColumnName)
+            {
+                if (TableName != null && TableName.Length > 0)
+                {
+                    ret += conn.EncloseFieldName(TableName);
+                    ret += ".";
+                }
+                ret += conn.EncloseFieldName(Object.ToString());
+            }
+            else if (ObjectType == ValueObjectType.Value)
+            {
+                ret += conn.PrepareValue(Object);
+            }
+            else ret += Object;
+
+            ret += ")";
+
+            return ret;
+        }
+    }
+}

dg.Sql/dg.Sql.csproj

@@ -84,6 +84,7 @@
     <Compile Include="Sql\Phrases\Math\Round.cs" />
     <Compile Include="Sql\Phrases\Quantitative\Avg.cs" />
     <Compile Include="Sql\Phrases\Quantitative\Aggregate.cs" />
+    <Compile Include="Sql\Phrases\Quantitative\CountDistinct.cs" />
     <Compile Include="Sql\Phrases\Quantitative\StandardDeviationOfPopulation.cs" />
     <Compile Include="Sql\Phrases\Quantitative\StandardDeviationOfSample.cs" />
     <Compile Include="Sql\Phrases\Quantitative\StandardVarianceOfSample.cs" />