diff --git a/chain.go b/chain.go
index 36380ce1..28ba14fe 100644
--- a/chain.go
+++ b/chain.go
@@ -7,9 +7,10 @@ import (
 )
 
 type Chain struct {
-	d     *DB
-	db    sql_common
-	value interface{}
+	d          *DB
+	db         sql_common
+	value      interface{}
+	debug_mode bool
 
 	Errors []error
 	Error  error
@@ -35,7 +36,7 @@ func (s *Chain) err(err error) error {
 	if err != nil {
 		s.Errors = append(s.Errors, err)
 		s.Error = err
-		warn(err)
+		s.warn(err)
 	}
 	return err
 }
@@ -257,6 +258,11 @@ func (s *Chain) Begin() *Chain {
 	return s
 }
 
+func (s *Chain) Debug() *Chain {
+	s.debug_mode = true
+	return s
+}
+
 func (s *Chain) Commit() *Chain {
 	if db, ok := s.db.(sql_tx); ok {
 		s.err(db.Commit())
diff --git a/do.go b/do.go
index f2c35fa7..32e974c7 100644
--- a/do.go
+++ b/do.go
@@ -77,8 +77,9 @@ func (s *Do) exec(sqls ...string) (err error) {
 		if len(sqls) > 0 {
 			s.sql = sqls[0]
 		}
+		now := time.Now()
 		_, err = s.db.Exec(s.sql, s.sqlVars...)
-		slog(s.sql, s.sqlVars...)
+		s.chain.slog(s.sql, now, s.sqlVars...)
 	}
 	return s.err(err)
 }
@@ -177,6 +178,7 @@ func (s *Do) create() (i interface{}) {
 	s.prepareCreateSql()
 
 	if !s.hasError() {
+		now := time.Now()
 		var id interface{}
 		if s.chain.driver() == "postgres" {
 			s.err(s.db.QueryRow(s.sql, s.sqlVars...).Scan(&id))
@@ -186,7 +188,7 @@ func (s *Do) create() (i interface{}) {
 				s.err(err)
 			}
 		}
-		slog(s.sql, s.sqlVars...)
+		s.chain.slog(s.sql, now, s.sqlVars...)
 
 		if !s.hasError() {
 			result := reflect.Indirect(reflect.ValueOf(s.value))
@@ -377,8 +379,9 @@ func (s *Do) query() {
 
 	s.prepareQuerySql()
 	if !s.hasError() {
+		now := time.Now()
 		rows, err := s.db.Query(s.sql, s.sqlVars...)
-		slog(s.sql, s.sqlVars...)
+		s.chain.slog(s.sql, now, s.sqlVars...)
 		if s.err(err) != nil {
 			return
 		}
@@ -433,8 +436,9 @@ func (s *Do) count(value interface{}) {
 
 	s.prepareQuerySql()
 	if !s.hasError() {
+		now := time.Now()
 		rows, err := s.db.Query(s.sql, s.sqlVars...)
-		slog(s.sql, s.sqlVars...)
+		s.chain.slog(s.sql, now, s.sqlVars...)
 		if s.err(err) != nil {
 			return
 		}
@@ -463,8 +467,9 @@ func (s *Do) pluck(column string, value interface{}) {
 	s.prepareQuerySql()
 
 	if !s.hasError() {
+		now := time.Now()
 		rows, err := s.db.Query(s.sql, s.sqlVars...)
-		slog(s.sql, s.sqlVars...)
+		s.chain.slog(s.sql, now, s.sqlVars...)
 		if s.err(err) != nil {
 			return
 		}
@@ -512,7 +517,7 @@ func (s *Do) buildWhereCondition(clause map[string]interface{}) (str string) {
 			id, _ := strconv.Atoi(value)
 			return s.primaryCondiation(s.addToVars(id))
 		} else {
-			str = "( " + value + " )"
+			str = "(" + value + ")"
 		}
 	case int, int64, int32:
 		return s.primaryCondiation(s.addToVars(query))
@@ -524,14 +529,14 @@ func (s *Do) buildWhereCondition(clause map[string]interface{}) (str string) {
 	case map[string]interface{}:
 		var sqls []string
 		for key, value := range query.(map[string]interface{}) {
-			sqls = append(sqls, fmt.Sprintf(" ( %v = %v ) ", key, s.addToVars(value)))
+			sqls = append(sqls, fmt.Sprintf("(%v = %v)", key, s.addToVars(value)))
 		}
 		return strings.Join(sqls, " AND ")
 	case interface{}:
 		m := &Model{data: query, do: s}
 		var sqls []string
 		for _, field := range m.columnsHasValue("other") {
-			sqls = append(sqls, fmt.Sprintf(" ( %v = %v ) ", field.DbName, s.addToVars(field.Value)))
+			sqls = append(sqls, fmt.Sprintf(" (%v = %v) ", field.DbName, s.addToVars(field.Value)))
 		}
 		return strings.Join(sqls, " AND ")
 	}
@@ -585,14 +590,14 @@ func (s *Do) buildNotCondition(clause map[string]interface{}) (str string) {
 	case map[string]interface{}:
 		var sqls []string
 		for key, value := range query.(map[string]interface{}) {
-			sqls = append(sqls, fmt.Sprintf(" ( %v <> %v ) ", key, s.addToVars(value)))
+			sqls = append(sqls, fmt.Sprintf("(%v <> %v)", key, s.addToVars(value)))
 		}
 		return strings.Join(sqls, " AND ")
 	case interface{}:
 		m := &Model{data: query, do: s}
 		var sqls []string
 		for _, field := range m.columnsHasValue("other") {
-			sqls = append(sqls, fmt.Sprintf(" ( %v <> %v ) ", field.DbName, s.addToVars(field.Value)))
+			sqls = append(sqls, fmt.Sprintf("(%v <> %v)", field.DbName, s.addToVars(field.Value)))
 		}
 		return strings.Join(sqls, " AND ")
 	}
@@ -654,7 +659,7 @@ func (s *Do) whereSql() (sql string) {
 	if len(primary_condiations) > 0 {
 		sql = "WHERE " + strings.Join(primary_condiations, " AND ")
 		if len(combined_conditions) > 0 {
-			sql = sql + " AND ( " + combined_conditions + " )"
+			sql = sql + " AND (" + combined_conditions + ")"
 		}
 	} else if len(combined_conditions) > 0 {
 		sql = "WHERE " + combined_conditions
@@ -664,7 +669,7 @@ func (s *Do) whereSql() (sql string) {
 
 func (s *Do) selectSql() string {
 	if len(s.selectStr) == 0 {
-		return " * "
+		return "*"
 	} else {
 		return s.selectStr
 	}
diff --git a/gorm_test.go b/gorm_test.go
index 8c38d61c..25938301 100644
--- a/gorm_test.go
+++ b/gorm_test.go
@@ -86,7 +86,7 @@ func init() {
 	// GRANT ALL ON gorm.* TO 'gorm'@'localhost';
 	// db, err = Open("mysql", "gorm:gorm@/gorm?charset=utf8&parseTime=True")
 	// db, err = Open("sqlite3", "/tmp/gorm.db")
-	db.LogMode(false)
+	db.LogMode(true)
 
 	if err != nil {
 		panic(fmt.Sprintf("No error should happen when connect database, but got %+v", err))
diff --git a/logger.go b/logger.go
index b23869f8..2caf9a5c 100644
--- a/logger.go
+++ b/logger.go
@@ -5,42 +5,32 @@ import (
 	"log"
 	"os"
 	"regexp"
+	"time"
 )
 
-var logger interface{}
-var logger_disabled bool
-
 type Logger interface {
 	Print(v ...interface{})
 }
 
-func print(level string, v ...interface{}) {
-	if logger_disabled && level != "debug" {
-		return
+func (s *Chain) print(level string, v ...interface{}) {
+	if s.d.log_mode || s.debug_mode || level == "debug" {
+		if _, ok := s.d.logger.(Logger); !ok {
+			fmt.Println("logger haven't been set, using os.Stdout")
+			s.d.logger = log.New(os.Stdout, "", 0)
+		}
+		args := []interface{}{level}
+		s.d.logger.(Logger).Print(append(args, v...))
 	}
-
-	var has_valid_logger bool
-	if logger, has_valid_logger = logger.(Logger); !has_valid_logger {
-		fmt.Println("logger haven't been set, using os.Stdout")
-		logger = log.New(os.Stdout, "", 0)
-	}
-
-	args := []interface{}{level}
-	logger.(Logger).Print(append(args, v...))
 }
 
-func warn(v ...interface{}) {
-	go print("warn", v...)
+func (s *Chain) warn(v ...interface{}) {
+	go s.print("warn", v...)
 }
 
-func info(v ...interface{}) {
-	go print("info", v...)
+func (s *Chain) slog(sql string, t time.Time, vars ...interface{}) {
+	go s.print("sql", time.Now().Sub(t), fmt.Sprintf(regexp.MustCompile(`\$\d|\?`).ReplaceAllString(sql, "'%v'"), vars...))
 }
 
-func slog(sql string, vars ...interface{}) {
-	go print("sql", fmt.Sprintf(regexp.MustCompile(`\$\d|\?`).ReplaceAllString(sql, "'%v'"), vars...))
-}
-
-func debug(v ...interface{}) {
-	go print("debug", v...)
+func (s *Chain) debug(v ...interface{}) {
+	go s.print("debug", v...)
 }
diff --git a/main.go b/main.go
index da8d33f1..f5f61401 100644
--- a/main.go
+++ b/main.go
@@ -5,8 +5,10 @@ import "database/sql"
 var singularTableName bool
 
 type DB struct {
-	db     sql_common
-	driver string
+	db       sql_common
+	driver   string
+	logger   Logger
+	log_mode bool
 }
 
 func Open(driver, source string) (db DB, err error) {
@@ -21,12 +23,12 @@ func (s *DB) SetPool(n int) {
 	}
 }
 
-func (s *DB) SetLogger(l interface{}) {
-	logger = l
+func (s *DB) SetLogger(l Logger) {
+	s.logger = l
 }
 
 func (s *DB) LogMode(b bool) {
-	logger_disabled = !b
+	s.log_mode = b
 }
 
 func (s *DB) SingularTable(result bool) {
@@ -125,6 +127,10 @@ func (s *DB) AutoMigrate(value interface{}) *Chain {
 	return s.buildChain().AutoMigrate(value)
 }
 
+func (s *DB) Debug() *Chain {
+	return s.buildChain().Debug()
+}
+
 func (s *DB) Begin() *Chain {
 	return s.buildChain().Begin()
 }