diff --git a/core/db.go b/core/db.go
index 9aa771ba..6845565d 100644
--- a/core/db.go
+++ b/core/db.go
@@ -77,6 +77,10 @@ type cacheStruct struct {
 	idx   int
 }
 
+var (
+	_ QueryExecuter = &DB{}
+)
+
 // DB is a wrap of sql.DB with extra contents
 type DB struct {
 	*sql.DB
diff --git a/core/interface.go b/core/interface.go
new file mode 100644
index 00000000..a5c8e4e2
--- /dev/null
+++ b/core/interface.go
@@ -0,0 +1,22 @@
+package core
+
+import (
+	"context"
+	"database/sql"
+)
+
+// Queryer represents an interface to query a SQL to get data from database
+type Queryer interface {
+	QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error)
+}
+
+// Executer represents an interface to execute a SQL
+type Executer interface {
+	ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error)
+}
+
+// QueryExecuter combines the Queryer and Executer
+type QueryExecuter interface {
+	Queryer
+	Executer
+}
diff --git a/core/stmt.go b/core/stmt.go
index 9d5954bd..4b1c7605 100644
--- a/core/stmt.go
+++ b/core/stmt.go
@@ -27,7 +27,7 @@ func (db *DB) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
 	var i int
 	query = re.ReplaceAllStringFunc(query, func(src string) string {
 		names[src[1:]] = i
-		i += 1
+		i++
 		return "?"
 	})
 
diff --git a/core/tx.go b/core/tx.go
index 07713267..99a8097d 100644
--- a/core/tx.go
+++ b/core/tx.go
@@ -12,6 +12,11 @@ import (
 	"xorm.io/xorm/log"
 )
 
+var (
+	_ QueryExecuter = &Tx{}
+)
+
+// Tx represents a transaction
 type Tx struct {
 	*sql.Tx
 	db *DB
@@ -50,7 +55,7 @@ func (tx *Tx) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
 	var i int
 	query = re.ReplaceAllStringFunc(query, func(src string) string {
 		names[src[1:]] = i
-		i += 1
+		i++
 		return "?"
 	})
 
diff --git a/dialects/dialect.go b/dialects/dialect.go
index 4fdf35e9..a3328e05 100644
--- a/dialects/dialect.go
+++ b/dialects/dialect.go
@@ -39,9 +39,8 @@ func (uri *URI) SetSchema(schema string) {
 
 // Dialect represents a kind of database
 type Dialect interface {
-	Init(*core.DB, *URI) error
+	Init(*URI) error
 	URI() *URI
-	DB() *core.DB
 	SQLType(*schemas.Column) string
 	FormatBytes(b []byte) string
 	DefaultSchema() string
@@ -52,18 +51,18 @@ type Dialect interface {
 
 	AutoIncrStr() string
 
-	GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error)
+	GetIndexes(queryer core.Queryer, ctx context.Context, tableName string) (map[string]*schemas.Index, error)
 	IndexCheckSQL(tableName, idxName string) (string, []interface{})
 	CreateIndexSQL(tableName string, index *schemas.Index) string
 	DropIndexSQL(tableName string, index *schemas.Index) string
 
-	GetTables(ctx context.Context) ([]*schemas.Table, error)
-	IsTableExist(ctx context.Context, tableName string) (bool, error)
+	GetTables(queryer core.Queryer, ctx context.Context) ([]*schemas.Table, error)
+	IsTableExist(queryer core.Queryer, ctx context.Context, tableName string) (bool, error)
 	CreateTableSQL(table *schemas.Table, tableName string) ([]string, bool)
 	DropTableSQL(tableName string) (string, bool)
 
-	GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error)
-	IsColumnExist(ctx context.Context, tableName string, colName string) (bool, error)
+	GetColumns(queryer core.Queryer, ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error)
+	IsColumnExist(queryer core.Queryer, ctx context.Context, tableName string, colName string) (bool, error)
 	AddColumnSQL(tableName string, col *schemas.Column) string
 	ModifyColumnSQL(tableName string, col *schemas.Column) string
 
@@ -75,7 +74,6 @@ type Dialect interface {
 
 // Base represents a basic dialect and all real dialects could embed this struct
 type Base struct {
-	db      *core.DB
 	dialect Dialect
 	uri     *URI
 	quoter  schemas.Quoter
@@ -85,16 +83,12 @@ func (b *Base) Quoter() schemas.Quoter {
 	return b.quoter
 }
 
-func (b *Base) DB() *core.DB {
-	return b.db
-}
-
 func (b *Base) DefaultSchema() string {
 	return ""
 }
 
-func (b *Base) Init(db *core.DB, dialect Dialect, uri *URI) error {
-	b.db, b.dialect, b.uri = db, dialect, uri
+func (b *Base) Init(dialect Dialect, uri *URI) error {
+	b.dialect, b.uri = dialect, uri
 	return nil
 }
 
@@ -160,8 +154,8 @@ func (db *Base) DropTableSQL(tableName string) (string, bool) {
 	return fmt.Sprintf("DROP TABLE IF EXISTS %s", quote(tableName)), true
 }
 
-func (db *Base) HasRecords(ctx context.Context, query string, args ...interface{}) (bool, error) {
-	rows, err := db.DB().QueryContext(ctx, query, args...)
+func (db *Base) HasRecords(queryer core.Queryer, ctx context.Context, query string, args ...interface{}) (bool, error) {
+	rows, err := queryer.QueryContext(ctx, query, args...)
 	if err != nil {
 		return false, err
 	}
@@ -173,7 +167,7 @@ func (db *Base) HasRecords(ctx context.Context, query string, args ...interface{
 	return false, nil
 }
 
-func (db *Base) IsColumnExist(ctx context.Context, tableName, colName string) (bool, error) {
+func (db *Base) IsColumnExist(queryer core.Queryer, ctx context.Context, tableName, colName string) (bool, error) {
 	quote := db.dialect.Quoter().Quote
 	query := fmt.Sprintf(
 		"SELECT %v FROM %v.%v WHERE %v = ? AND %v = ? AND %v = ?",
@@ -184,7 +178,7 @@ func (db *Base) IsColumnExist(ctx context.Context, tableName, colName string) (b
 		quote("TABLE_NAME"),
 		quote("COLUMN_NAME"),
 	)
-	return db.HasRecords(ctx, query, db.uri.DBName, tableName, colName)
+	return db.HasRecords(queryer, ctx, query, db.uri.DBName, tableName, colName)
 }
 
 func (db *Base) AddColumnSQL(tableName string, col *schemas.Column) string {
diff --git a/dialects/driver.go b/dialects/driver.go
index 89d21bfc..ae3afe42 100644
--- a/dialects/driver.go
+++ b/dialects/driver.go
@@ -6,8 +6,6 @@ package dialects
 
 import (
 	"fmt"
-
-	"xorm.io/xorm/core"
 )
 
 type Driver interface {
@@ -53,11 +51,7 @@ func OpenDialect(driverName, connstr string) (Dialect, error) {
 		return nil, fmt.Errorf("Unsupported dialect type: %v", uri.DBType)
 	}
 
-	db, err := core.Open(driverName, connstr)
-	if err != nil {
-		return nil, err
-	}
-	dialect.Init(db, uri)
+	dialect.Init(uri)
 
 	return dialect, nil
 }
diff --git a/dialects/mssql.go b/dialects/mssql.go
index dd3f4247..92457ff9 100644
--- a/dialects/mssql.go
+++ b/dialects/mssql.go
@@ -212,9 +212,9 @@ type mssql struct {
 	Base
 }
 
-func (db *mssql) Init(d *core.DB, uri *URI) error {
+func (db *mssql) Init(uri *URI) error {
 	db.quoter = mssqlQuoter
-	return db.Base.Init(d, db, uri)
+	return db.Base.Init(db, uri)
 }
 
 func (db *mssql) SQLType(c *schemas.Column) string {
@@ -319,18 +319,18 @@ func (db *mssql) IndexCheckSQL(tableName, idxName string) (string, []interface{}
 	return sql, args
 }
 
-func (db *mssql) IsColumnExist(ctx context.Context, tableName, colName string) (bool, error) {
+func (db *mssql) IsColumnExist(queryer core.Queryer, ctx context.Context, tableName, colName string) (bool, error) {
 	query := `SELECT "COLUMN_NAME" FROM "INFORMATION_SCHEMA"."COLUMNS" WHERE "TABLE_NAME" = ? AND "COLUMN_NAME" = ?`
 
-	return db.HasRecords(ctx, query, tableName, colName)
+	return db.HasRecords(queryer, ctx, query, tableName, colName)
 }
 
-func (db *mssql) IsTableExist(ctx context.Context, tableName string) (bool, error) {
+func (db *mssql) IsTableExist(queryer core.Queryer, ctx context.Context, tableName string) (bool, error) {
 	sql := "select * from sysobjects where id = object_id(N'" + tableName + "') and OBJECTPROPERTY(id, N'IsUserTable') = 1"
-	return db.HasRecords(ctx, sql)
+	return db.HasRecords(queryer, ctx, sql)
 }
 
-func (db *mssql) GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
+func (db *mssql) GetColumns(queryer core.Queryer, ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
 	args := []interface{}{}
 	s := `select a.name as name, b.name as ctype,a.max_length,a.precision,a.scale,a.is_nullable as nullable,
 		  "default_is_null" = (CASE WHEN c.text is null THEN 1 ELSE 0 END),
@@ -346,7 +346,7 @@ func (db *mssql) GetColumns(ctx context.Context, tableName string) ([]string, ma
 		) as p on p.object_id = a.object_id AND p.column_id = a.column_id
           where a.object_id=object_id('` + tableName + `')`
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -401,11 +401,11 @@ func (db *mssql) GetColumns(ctx context.Context, tableName string) ([]string, ma
 	return colSeq, cols, nil
 }
 
-func (db *mssql) GetTables(ctx context.Context) ([]*schemas.Table, error) {
+func (db *mssql) GetTables(queryer core.Queryer, ctx context.Context) ([]*schemas.Table, error) {
 	args := []interface{}{}
 	s := `select name from sysobjects where xtype ='U'`
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -425,7 +425,7 @@ func (db *mssql) GetTables(ctx context.Context) ([]*schemas.Table, error) {
 	return tables, nil
 }
 
-func (db *mssql) GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
+func (db *mssql) GetIndexes(queryer core.Queryer, ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
 	args := []interface{}{tableName}
 	s := `SELECT
 IXS.NAME                    AS  [INDEX_NAME],
@@ -439,7 +439,7 @@ AND IXCS.COLUMN_ID=C.COLUMN_ID
 WHERE IXS.TYPE_DESC='NONCLUSTERED' and OBJECT_NAME(IXS.OBJECT_ID) =?
 `
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/dialects/mysql.go b/dialects/mysql.go
index b7598680..289e0ec7 100644
--- a/dialects/mysql.go
+++ b/dialects/mysql.go
@@ -179,9 +179,9 @@ type mysql struct {
 	rowFormat         string
 }
 
-func (db *mysql) Init(d *core.DB, uri *URI) error {
+func (db *mysql) Init(uri *URI) error {
 	db.quoter = mysqlQuoter
-	return db.Base.Init(d, db, uri)
+	return db.Base.Init(db, uri)
 }
 
 func (db *mysql) SetParams(params map[string]string) {
@@ -286,9 +286,9 @@ func (db *mysql) IndexCheckSQL(tableName, idxName string) (string, []interface{}
 	return sql, args
 }
 
-func (db *mysql) IsTableExist(ctx context.Context, tableName string) (bool, error) {
+func (db *mysql) IsTableExist(queryer core.Queryer, ctx context.Context, tableName string) (bool, error) {
 	sql := "SELECT `TABLE_NAME` from `INFORMATION_SCHEMA`.`TABLES` WHERE `TABLE_SCHEMA`=? and `TABLE_NAME`=?"
-	return db.HasRecords(ctx, sql, db.uri.DBName, tableName)
+	return db.HasRecords(queryer, ctx, sql, db.uri.DBName, tableName)
 }
 
 func (db *mysql) AddColumnSQL(tableName string, col *schemas.Column) string {
@@ -301,12 +301,12 @@ func (db *mysql) AddColumnSQL(tableName string, col *schemas.Column) string {
 	return sql
 }
 
-func (db *mysql) GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
+func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
 	args := []interface{}{db.uri.DBName, tableName}
 	s := "SELECT `COLUMN_NAME`, `IS_NULLABLE`, `COLUMN_DEFAULT`, `COLUMN_TYPE`," +
 		" `COLUMN_KEY`, `EXTRA`,`COLUMN_COMMENT` FROM `INFORMATION_SCHEMA`.`COLUMNS` WHERE `TABLE_SCHEMA` = ? AND `TABLE_NAME` = ?"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -411,12 +411,12 @@ func (db *mysql) GetColumns(ctx context.Context, tableName string) ([]string, ma
 	return colSeq, cols, nil
 }
 
-func (db *mysql) GetTables(ctx context.Context) ([]*schemas.Table, error) {
+func (db *mysql) GetTables(queryer core.Queryer, ctx context.Context) ([]*schemas.Table, error) {
 	args := []interface{}{db.uri.DBName}
 	s := "SELECT `TABLE_NAME`, `ENGINE`, `AUTO_INCREMENT`, `TABLE_COMMENT` from " +
 		"`INFORMATION_SCHEMA`.`TABLES` WHERE `TABLE_SCHEMA`=? AND (`ENGINE`='MyISAM' OR `ENGINE` = 'InnoDB' OR `ENGINE` = 'TokuDB')"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -459,11 +459,11 @@ func (db *mysql) SetQuotePolicy(quotePolicy QuotePolicy) {
 	}
 }
 
-func (db *mysql) GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
+func (db *mysql) GetIndexes(queryer core.Queryer, ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
 	args := []interface{}{db.uri.DBName, tableName}
 	s := "SELECT `INDEX_NAME`, `NON_UNIQUE`, `COLUMN_NAME` FROM `INFORMATION_SCHEMA`.`STATISTICS` WHERE `TABLE_SCHEMA` = ? AND `TABLE_NAME` = ?"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/dialects/oracle.go b/dialects/oracle.go
index 466b6a45..db823e95 100644
--- a/dialects/oracle.go
+++ b/dialects/oracle.go
@@ -506,9 +506,9 @@ type oracle struct {
 	Base
 }
 
-func (db *oracle) Init(d *core.DB, uri *URI) error {
+func (db *oracle) Init(uri *URI) error {
 	db.quoter = oracleQuoter
-	return db.Base.Init(d, db, uri)
+	return db.Base.Init(db, uri)
 }
 
 func (db *oracle) SQLType(c *schemas.Column) string {
@@ -611,23 +611,23 @@ func (db *oracle) IndexCheckSQL(tableName, idxName string) (string, []interface{
 		`WHERE TABLE_NAME = :1 AND INDEX_NAME = :2`, args
 }
 
-func (db *oracle) IsTableExist(ctx context.Context, tableName string) (bool, error) {
-	return db.HasRecords(ctx, `SELECT table_name FROM user_tables WHERE table_name = :1`, tableName)
+func (db *oracle) IsTableExist(queryer core.Queryer, ctx context.Context, tableName string) (bool, error) {
+	return db.HasRecords(queryer, ctx, `SELECT table_name FROM user_tables WHERE table_name = :1`, tableName)
 }
 
-func (db *oracle) IsColumnExist(ctx context.Context, tableName, colName string) (bool, error) {
+func (db *oracle) IsColumnExist(queryer core.Queryer, ctx context.Context, tableName, colName string) (bool, error) {
 	args := []interface{}{tableName, colName}
 	query := "SELECT column_name FROM USER_TAB_COLUMNS WHERE table_name = :1" +
 		" AND column_name = :2"
-	return db.HasRecords(ctx, query, args...)
+	return db.HasRecords(queryer, ctx, query, args...)
 }
 
-func (db *oracle) GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
+func (db *oracle) GetColumns(queryer core.Queryer, ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
 	args := []interface{}{tableName}
 	s := "SELECT column_name,data_default,data_type,data_length,data_precision,data_scale," +
 		"nullable FROM USER_TAB_COLUMNS WHERE table_name = :1"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -719,11 +719,11 @@ func (db *oracle) GetColumns(ctx context.Context, tableName string) ([]string, m
 	return colSeq, cols, nil
 }
 
-func (db *oracle) GetTables(ctx context.Context) ([]*schemas.Table, error) {
+func (db *oracle) GetTables(queryer core.Queryer, ctx context.Context) ([]*schemas.Table, error) {
 	args := []interface{}{}
 	s := "SELECT table_name FROM user_tables"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -742,12 +742,12 @@ func (db *oracle) GetTables(ctx context.Context) ([]*schemas.Table, error) {
 	return tables, nil
 }
 
-func (db *oracle) GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
+func (db *oracle) GetIndexes(queryer core.Queryer, ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
 	args := []interface{}{tableName}
 	s := "SELECT t.column_name,i.uniqueness,i.index_name FROM user_ind_columns t,user_indexes i " +
 		"WHERE t.index_name = i.index_name and t.table_name = i.table_name and t.table_name =:1"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/dialects/postgres.go b/dialects/postgres.go
index 0a851fe2..a83c3a5c 100644
--- a/dialects/postgres.go
+++ b/dialects/postgres.go
@@ -776,9 +776,9 @@ type postgres struct {
 	Base
 }
 
-func (db *postgres) Init(d *core.DB, uri *URI) error {
+func (db *postgres) Init(uri *URI) error {
 	db.quoter = postgresQuoter
-	err := db.Base.Init(d, db, uri)
+	err := db.Base.Init(db, uri)
 	if err != nil {
 		return err
 	}
@@ -942,12 +942,12 @@ func (db *postgres) IndexCheckSQL(tableName, idxName string) (string, []interfac
 		`WHERE schemaname = ? AND tablename = ? AND indexname = ?`, args
 }
 
-func (db *postgres) IsTableExist(ctx context.Context, tableName string) (bool, error) {
+func (db *postgres) IsTableExist(queryer core.Queryer, ctx context.Context, tableName string) (bool, error) {
 	if len(db.uri.Schema) == 0 {
-		return db.HasRecords(ctx, `SELECT tablename FROM pg_tables WHERE tablename = $1`, tableName)
+		return db.HasRecords(queryer, ctx, `SELECT tablename FROM pg_tables WHERE tablename = $1`, tableName)
 	}
 
-	return db.HasRecords(ctx, `SELECT tablename FROM pg_tables WHERE schemaname = $1 AND tablename = $2`,
+	return db.HasRecords(queryer, ctx, `SELECT tablename FROM pg_tables WHERE schemaname = $1 AND tablename = $2`,
 		db.uri.Schema, tableName)
 }
 
@@ -980,7 +980,7 @@ func (db *postgres) DropIndexSQL(tableName string, index *schemas.Index) string
 	return fmt.Sprintf("DROP INDEX %v", db.Quoter().Quote(idxName))
 }
 
-func (db *postgres) IsColumnExist(ctx context.Context, tableName, colName string) (bool, error) {
+func (db *postgres) IsColumnExist(queryer core.Queryer, ctx context.Context, tableName, colName string) (bool, error) {
 	args := []interface{}{db.uri.Schema, tableName, colName}
 	query := "SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE table_schema = $1 AND table_name = $2" +
 		" AND column_name = $3"
@@ -990,7 +990,7 @@ func (db *postgres) IsColumnExist(ctx context.Context, tableName, colName string
 			" AND column_name = $2"
 	}
 
-	rows, err := db.DB().QueryContext(ctx, query, args...)
+	rows, err := queryer.QueryContext(ctx, query, args...)
 	if err != nil {
 		return false, err
 	}
@@ -999,7 +999,7 @@ func (db *postgres) IsColumnExist(ctx context.Context, tableName, colName string
 	return rows.Next(), nil
 }
 
-func (db *postgres) GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
+func (db *postgres) GetColumns(queryer core.Queryer, ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
 	args := []interface{}{db.uri.Schema, tableName, db.uri.Schema}
 	s := `SELECT column_name, column_default, is_nullable, data_type, character_maximum_length,
     CASE WHEN p.contype = 'p' THEN true ELSE false END AS primarykey,
@@ -1013,7 +1013,7 @@ FROM pg_attribute f
     LEFT JOIN INFORMATION_SCHEMA.COLUMNS s ON s.column_name=f.attname AND c.relname=s.table_name
 WHERE n.nspname= $1 AND c.relkind = 'r'::char AND c.relname = $2 AND s.table_schema = $3 AND f.attnum > 0 ORDER BY f.attnum;`
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -1132,7 +1132,7 @@ WHERE n.nspname= $1 AND c.relkind = 'r'::char AND c.relname = $2 AND s.table_sch
 	return colSeq, cols, nil
 }
 
-func (db *postgres) GetTables(ctx context.Context) ([]*schemas.Table, error) {
+func (db *postgres) GetTables(queryer core.Queryer, ctx context.Context) ([]*schemas.Table, error) {
 	args := []interface{}{}
 	s := "SELECT tablename FROM pg_tables"
 	if len(db.uri.Schema) != 0 {
@@ -1140,7 +1140,7 @@ func (db *postgres) GetTables(ctx context.Context) ([]*schemas.Table, error) {
 		s = s + " WHERE schemaname = $1"
 	}
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -1171,7 +1171,7 @@ func getIndexColName(indexdef string) []string {
 	return colNames
 }
 
-func (db *postgres) GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
+func (db *postgres) GetIndexes(queryer core.Queryer, ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
 	args := []interface{}{tableName}
 	s := fmt.Sprintf("SELECT indexname, indexdef FROM pg_indexes WHERE tablename=$1")
 	if len(db.uri.Schema) != 0 {
@@ -1179,7 +1179,7 @@ func (db *postgres) GetIndexes(ctx context.Context, tableName string) (map[strin
 		s = s + " AND schemaname=$2"
 	}
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/dialects/sqlite3.go b/dialects/sqlite3.go
index 710babe6..0e95ebc7 100644
--- a/dialects/sqlite3.go
+++ b/dialects/sqlite3.go
@@ -151,9 +151,9 @@ type sqlite3 struct {
 	Base
 }
 
-func (db *sqlite3) Init(d *core.DB, uri *URI) error {
+func (db *sqlite3) Init(uri *URI) error {
 	db.quoter = sqlite3Quoter
-	return db.Base.Init(d, db, uri)
+	return db.Base.Init(db, uri)
 }
 
 func (db *sqlite3) SetQuotePolicy(quotePolicy QuotePolicy) {
@@ -225,8 +225,8 @@ func (db *sqlite3) IndexCheckSQL(tableName, idxName string) (string, []interface
 	return "SELECT name FROM sqlite_master WHERE type='index' and name = ?", args
 }
 
-func (db *sqlite3) IsTableExist(ctx context.Context, tableName string) (bool, error) {
-	return db.HasRecords(ctx, "SELECT name FROM sqlite_master WHERE type='table' and name = ?", tableName)
+func (db *sqlite3) IsTableExist(queryer core.Queryer, ctx context.Context, tableName string) (bool, error) {
+	return db.HasRecords(queryer, ctx, "SELECT name FROM sqlite_master WHERE type='table' and name = ?", tableName)
 }
 
 func (db *sqlite3) DropIndexSQL(tableName string, index *schemas.Index) string {
@@ -286,9 +286,9 @@ func (db *sqlite3) ForUpdateSQL(query string) string {
 	return query
 }
 
-func (db *sqlite3) IsColumnExist(ctx context.Context, tableName, colName string) (bool, error) {
+func (db *sqlite3) IsColumnExist(queryer core.Queryer, ctx context.Context, tableName, colName string) (bool, error) {
 	query := "SELECT * FROM " + tableName + " LIMIT 0"
-	rows, err := db.DB().QueryContext(ctx, query)
+	rows, err := queryer.QueryContext(ctx, query)
 	if err != nil {
 		return false, err
 	}
@@ -370,11 +370,11 @@ func parseString(colStr string) (*schemas.Column, error) {
 	return col, nil
 }
 
-func (db *sqlite3) GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
+func (db *sqlite3) GetColumns(queryer core.Queryer, ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error) {
 	args := []interface{}{tableName}
 	s := "SELECT sql FROM sqlite_master WHERE type='table' and name = ?"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -427,11 +427,11 @@ func (db *sqlite3) GetColumns(ctx context.Context, tableName string) ([]string,
 	return colSeq, cols, nil
 }
 
-func (db *sqlite3) GetTables(ctx context.Context) ([]*schemas.Table, error) {
+func (db *sqlite3) GetTables(queryer core.Queryer, ctx context.Context) ([]*schemas.Table, error) {
 	args := []interface{}{}
 	s := "SELECT name FROM sqlite_master WHERE type='table'"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -452,11 +452,11 @@ func (db *sqlite3) GetTables(ctx context.Context) ([]*schemas.Table, error) {
 	return tables, nil
 }
 
-func (db *sqlite3) GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
+func (db *sqlite3) GetIndexes(queryer core.Queryer, ctx context.Context, tableName string) (map[string]*schemas.Index, error) {
 	args := []interface{}{tableName}
 	s := "SELECT sql FROM sqlite_master WHERE type='index' and tbl_name = ?"
 
-	rows, err := db.DB().QueryContext(ctx, s, args...)
+	rows, err := queryer.QueryContext(ctx, s, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/engine.go b/engine.go
index 4694e1c0..dd34fe1b 100644
--- a/engine.go
+++ b/engine.go
@@ -35,6 +35,7 @@ type Engine struct {
 	engineGroup    *EngineGroup
 	logger         log.ContextLogger
 	tagParser      *tags.Parser
+	db             *core.DB
 
 	driverName     string
 	dataSourceName string
@@ -211,7 +212,7 @@ func (engine *Engine) NewDB() (*core.DB, error) {
 
 // DB return the wrapper of sql.DB
 func (engine *Engine) DB() *core.DB {
-	return engine.dialect.DB()
+	return engine.db
 }
 
 // Dialect return database dialect
@@ -267,14 +268,14 @@ func (engine *Engine) NoAutoCondition(no ...bool) *Session {
 }
 
 func (engine *Engine) loadTableInfo(table *schemas.Table) error {
-	colSeq, cols, err := engine.dialect.GetColumns(engine.defaultContext, table.Name)
+	colSeq, cols, err := engine.dialect.GetColumns(engine.db, engine.defaultContext, table.Name)
 	if err != nil {
 		return err
 	}
 	for _, name := range colSeq {
 		table.AddColumn(cols[name])
 	}
-	indexes, err := engine.dialect.GetIndexes(engine.defaultContext, table.Name)
+	indexes, err := engine.dialect.GetIndexes(engine.db, engine.defaultContext, table.Name)
 	if err != nil {
 		return err
 	}
@@ -301,7 +302,7 @@ func (engine *Engine) loadTableInfo(table *schemas.Table) error {
 
 // DBMetas Retrieve all tables, columns, indexes' informations from database.
 func (engine *Engine) DBMetas() ([]*schemas.Table, error) {
-	tables, err := engine.dialect.GetTables(engine.defaultContext)
+	tables, err := engine.dialect.GetTables(engine.db, engine.defaultContext)
 	if err != nil {
 		return nil, err
 	}
@@ -361,7 +362,7 @@ func (engine *Engine) dumpTables(tables []*schemas.Table, w io.Writer, tp ...sch
 
 		uri := engine.dialect.URI()
 		destURI := *uri
-		dstDialect.Init(nil, &destURI)
+		dstDialect.Init(&destURI)
 	}
 
 	_, err := io.WriteString(w, fmt.Sprintf("/*Generated by xorm %s, from %s to %s*/\n\n",
@@ -911,7 +912,7 @@ func (engine *Engine) Sync(beans ...interface{}) error {
 			}
 		} else {
 			for _, col := range table.Columns() {
-				isExist, err := engine.dialect.IsColumnExist(session.ctx, tableNameNoSchema, col.Name)
+				isExist, err := engine.dialect.IsColumnExist(engine.db, session.ctx, tableNameNoSchema, col.Name)
 				if err != nil {
 					return err
 				}
diff --git a/engine_group.go b/engine_group.go
index 868d4dc9..d557645e 100644
--- a/engine_group.go
+++ b/engine_group.go
@@ -161,17 +161,17 @@ func (eg *EngineGroup) SetMapper(mapper names.Mapper) {
 
 // SetMaxIdleConns set the max idle connections on pool, default is 2
 func (eg *EngineGroup) SetMaxIdleConns(conns int) {
-	eg.Engine.dialect.DB().SetMaxIdleConns(conns)
+	eg.Engine.DB().SetMaxIdleConns(conns)
 	for i := 0; i < len(eg.slaves); i++ {
-		eg.slaves[i].dialect.DB().SetMaxIdleConns(conns)
+		eg.slaves[i].DB().SetMaxIdleConns(conns)
 	}
 }
 
 // SetMaxOpenConns is only available for go 1.2+
 func (eg *EngineGroup) SetMaxOpenConns(conns int) {
-	eg.Engine.dialect.DB().SetMaxOpenConns(conns)
+	eg.Engine.DB().SetMaxOpenConns(conns)
 	for i := 0; i < len(eg.slaves); i++ {
-		eg.slaves[i].dialect.DB().SetMaxOpenConns(conns)
+		eg.slaves[i].DB().SetMaxOpenConns(conns)
 	}
 }
 
diff --git a/session.go b/session.go
index 4842883b..6b8bfbaf 100644
--- a/session.go
+++ b/session.go
@@ -99,7 +99,7 @@ func (session *Session) Init() {
 		session.engine.tagParser,
 		session.engine.DatabaseTZ,
 	)
-
+	session.db = session.engine.db
 	session.isAutoCommit = true
 	session.isCommitedOrRollbacked = false
 	session.isAutoClose = false
@@ -140,6 +140,13 @@ func (session *Session) Close() {
 	}
 }
 
+func (session *Session) getQueryer() core.Queryer {
+	if session.tx != nil {
+		return session.tx
+	}
+	return session.db
+}
+
 // ContextCache enable context cache or not
 func (session *Session) ContextCache(context contexts.ContextCache) *Session {
 	session.statement.SetContextCache(context)
diff --git a/session_schema.go b/session_schema.go
index 84eb586e..9ccf8abe 100644
--- a/session_schema.go
+++ b/session_schema.go
@@ -134,7 +134,7 @@ func (session *Session) dropTable(beanOrTableName interface{}) error {
 	tableName := session.engine.TableName(beanOrTableName)
 	sqlStr, checkIfExist := session.engine.dialect.DropTableSQL(session.engine.TableName(tableName, true))
 	if !checkIfExist {
-		exist, err := session.engine.dialect.IsTableExist(session.ctx, tableName)
+		exist, err := session.engine.dialect.IsTableExist(session.getQueryer(), session.ctx, tableName)
 		if err != nil {
 			return err
 		}
@@ -160,7 +160,7 @@ func (session *Session) IsTableExist(beanOrTableName interface{}) (bool, error)
 }
 
 func (session *Session) isTableExist(tableName string) (bool, error) {
-	return session.engine.dialect.IsTableExist(session.ctx, tableName)
+	return session.engine.dialect.IsTableExist(session.getQueryer(), session.ctx, tableName)
 }
 
 // IsTableEmpty if table have any records
@@ -187,7 +187,7 @@ func (session *Session) isTableEmpty(tableName string) (bool, error) {
 
 // find if index is exist according cols
 func (session *Session) isIndexExist2(tableName string, cols []string, unique bool) (bool, error) {
-	indexes, err := session.engine.dialect.GetIndexes(session.ctx, tableName)
+	indexes, err := session.engine.dialect.GetIndexes(session.getQueryer(), session.ctx, tableName)
 	if err != nil {
 		return false, err
 	}
@@ -233,7 +233,7 @@ func (session *Session) Sync2(beans ...interface{}) error {
 		defer session.Close()
 	}
 
-	tables, err := engine.dialect.GetTables(session.ctx)
+	tables, err := engine.dialect.GetTables(session.getQueryer(), session.ctx)
 	if err != nil {
 		return err
 	}
diff --git a/xorm.go b/xorm.go
index 2025522f..e9cd7415 100644
--- a/xorm.go
+++ b/xorm.go
@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"xorm.io/xorm/caches"
+	"xorm.io/xorm/core"
 	"xorm.io/xorm/dialects"
 	"xorm.io/xorm/log"
 	"xorm.io/xorm/names"
@@ -32,6 +33,11 @@ func NewEngine(driverName string, dataSourceName string) (*Engine, error) {
 		return nil, err
 	}
 
+	db, err := core.Open(driverName, dataSourceName)
+	if err != nil {
+		return nil, err
+	}
+
 	cacherMgr := caches.NewManager()
 	mapper := names.NewCacheMapper(new(names.SnakeMapper))
 	tagParser := tags.NewParser("xorm", dialect, mapper, mapper, cacherMgr)
@@ -44,6 +50,7 @@ func NewEngine(driverName string, dataSourceName string) (*Engine, error) {
 		tagParser:      tagParser,
 		driverName:     driverName,
 		dataSourceName: dataSourceName,
+		db:             db,
 	}
 
 	if dialect.URI().DBType == schemas.SQLITE {