diff --git a/sqlor/dbpools.py b/sqlor/dbpools.py
index ed018d5..de0aee2 100644
--- a/sqlor/dbpools.py
+++ b/sqlor/dbpools.py
@@ -192,7 +192,12 @@ class DBPools:
 		sqlor = await self.getSqlor(name)
 		try:
 			yield sqlor
+		except:
+			if sqlor.dataChanged:
+				sqlor.rollback()
 		finally:
+			if sqlor.dataChanged:
+				sqlor.commit()
 			await self.freeSqlor(sqlor)
 	
 	async def _aquireConn(self,dbname):
diff --git a/sqlor/sor.py b/sqlor/sor.py
index 7fddb65..cbef5e4 100644
--- a/sqlor/sor.py
+++ b/sqlor/sor.py
@@ -63,6 +63,7 @@ class SQLor(object):
 		self.writer = None
 		self.convfuncs = {}
 		self.cc = ConditionConvert()
+		self.dataChanged = False
 	
 	def setCursor(self,async_mode,conn,cur):
 		self.async_mode = async_mode
@@ -197,10 +198,28 @@ class SQLor(object):
 		
 		return (m_sql,newdata)
 		
+	def getSQLType(self,sql):
+		"""
+		return one of "qry", "dml" and "ddl"
+		ddl change the database schema
+		dml change the database data
+		qry query data
+		"""
+		
+		a = sql.lstrip(' \t\n\r')
+		a = a.lower()
+		al = a.split(' ')
+		if al[0] == 'select':
+			return 'qry'
+		if al[0] in ['update','delete','insert']:
+			return 'dml'
+		return 'ddl'
+		
 	async def execute(self,sql,value,callback,**kwargs):
+		sqltype = self.getSqlType(sql)
 		cur = self.cursor()
 		await self.runVarSQL(cur,sql,value)
-		if callback is not None:
+		if sqltype == 'qry' and callback is not None:
 			fields = [ i[0].lower() for i in cur.description ]
 			rec = None
 			if self.async_mode:
@@ -217,7 +236,8 @@ class SQLor(object):
 					rec = await cur.fetchone()
 				else:
 					rec = cur.fetchone()
-		
+		if sqltype == 'dml':
+			self.dataChanged = True
 
 	async def executemany(self,sql,values):
 		cur = self.cursor()
@@ -282,10 +302,7 @@ class SQLor(object):
 		return await self.execute(sql,{},lambda x:ret.append(x))
 
 	def isSelectSql(self,sql):
-		i = 0
-		while sql[i] in "\r\n \t":
-			i = i + 1
-		return sql.lower().startswith('select ')
+		return self.getSqlType(sql) == 'qry'
 
 	def getSQLfromDesc(self,desc):
 		sql = ''
@@ -455,4 +472,10 @@ class SQLor(object):
 			desc['validation'].append(idx)		
 		return desc
 	
-				
+	def rollback(self):
+		self.conn.rollback()
+		self.dataChanged = False
+
+	def commit(self):
+		self.conn.commit()
+		self.datachanged = False