NH-3749 - Remove unnecessary comma in CREATE TABLE statement (#1651)

Fixes #1037

Author: lesnyh

src/NHibernate.Test/NHSpecificTest/NH3749/Fixture.cs

@@ -0,0 +1,30 @@
+using NUnit.Framework;
+using NHibernate.Mapping;
+
+namespace NHibernate.Test.NHSpecificTest.NH3749
+{
+	[TestFixture]
+	public class Fixture
+	{
+		[Test]
+		public void SupportsNotNullUniqueFalse()
+		{
+			Table tbl = new Table();
+			tbl.Name = "Table";
+
+			Column column = new Column("Column");
+			column.IsNullable = true;
+
+			UniqueKey uk = new UniqueKey { Name = "UniqueKey", Table = tbl };
+			uk.Columns.Add(column);
+
+			tbl.AddUniqueKey(uk);
+			
+			Dialect.Dialect dialect = new TestDialect();
+
+			string sql = tbl.SqlCreateString(dialect, null, "", "");
+
+			Assert.IsFalse(sql.Contains(",)"), "Create command has unnecessary comma: " + sql);
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/NH3749/TestDialect.cs

@@ -0,0 +1,11 @@
+
+namespace NHibernate.Test.NHSpecificTest.NH3749
+{
+	public class TestDialect : Dialect.Dialect
+	{
+		public override bool SupportsNotNullUnique
+		{
+			get { return false; }
+		}
+	}
+}

src/NHibernate/Mapping/Table.cs

@@ -434,7 +434,11 @@ public string SqlCreateString(Dialect.Dialect dialect, IMapping p, string defaul
 
 			foreach (UniqueKey uk in UniqueKeyIterator)
 			{
-				buf.Append(',').Append(uk.SqlConstraintString(dialect));
+				string ukSql = uk.SqlConstraintString(dialect);
+				if (!string.IsNullOrEmpty(ukSql))
+				{
+					buf.Append(',').Append(ukSql);
+				}
 			}
 
 			if (dialect.SupportsTableCheck)