[SPARK-10856][SQL] Mapping TimestampType to DATETIME for SQL Server jdbc dialect

JIRA: https://issues.apache.org/jira/browse/SPARK-10856

For Microsoft SQL Server, TimestampType should be mapped to DATETIME instead of TIMESTAMP.

Related information for the datatype mapping: https://msdn.microsoft.com/en-us/library/ms378878(v=sql.110).aspx

Author: Liang-Chi Hsieh <viirya@appier.com>

Closes #8978 from viirya/mysql-jdbc-timestamp.

sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala

@@ -277,4 +277,9 @@ case object MsSqlServerDialect extends JdbcDialect {
       Some(StringType)
     } else None
   }
+
+  override def getJDBCType(dt: DataType): Option[JdbcType] = dt match {
+    case TimestampType => Some(JdbcType("DATETIME", java.sql.Types.TIMESTAMP))
+    case _ => None
+  }
 }