diff --git a/mysql/driver/connection.go b/mysql/driver/connection.go
index 02ad2ce..9c0a94a 100644
--- a/mysql/driver/connection.go
+++ b/mysql/driver/connection.go
@@ -12,7 +12,6 @@ import (
 	"context"
 	"database/sql/driver"
 	"net"
-	"strconv"
 	"strings"
 	"time"
 )
@@ -219,157 +218,6 @@ func (mc *mysqlConn) error() error {
 	return nil
 }
 
-func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (string, error) {
-	// Number of ? should be same to len(args)
-	if strings.Count(query, "?") != len(args) {
-		return "", driver.ErrSkip
-	}
-
-	buf := mc.buf.takeCompleteBuffer()
-	if buf == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return "", ErrInvalidConn
-	}
-	buf = buf[:0]
-	argPos := 0
-
-	for i := 0; i < len(query); i++ {
-		q := strings.IndexByte(query[i:], '?')
-		if q == -1 {
-			buf = append(buf, query[i:]...)
-			break
-		}
-		buf = append(buf, query[i:i+q]...)
-		i += q
-
-		arg := args[argPos]
-		argPos++
-
-		if arg == nil {
-			buf = append(buf, "NULL"...)
-			continue
-		}
-
-		switch v := arg.(type) {
-		case int64:
-			buf = strconv.AppendInt(buf, v, 10)
-		case float64:
-			buf = strconv.AppendFloat(buf, v, 'g', -1, 64)
-		case bool:
-			if v {
-				buf = append(buf, '1')
-			} else {
-				buf = append(buf, '0')
-			}
-		case time.Time:
-			if v.IsZero() {
-				buf = append(buf, "'0000-00-00'"...)
-			} else {
-				v := v.In(mc.cfg.Loc)
-				v = v.Add(time.Nanosecond * 500) // To round under microsecond
-				year := v.Year()
-				year100 := year / 100
-				year1 := year % 100
-				month := v.Month()
-				day := v.Day()
-				hour := v.Hour()
-				minute := v.Minute()
-				second := v.Second()
-				micro := v.Nanosecond() / 1000
-
-				buf = append(buf, []byte{
-					'\'',
-					digits10[year100], digits01[year100],
-					digits10[year1], digits01[year1],
-					'-',
-					digits10[month], digits01[month],
-					'-',
-					digits10[day], digits01[day],
-					' ',
-					digits10[hour], digits01[hour],
-					':',
-					digits10[minute], digits01[minute],
-					':',
-					digits10[second], digits01[second],
-				}...)
-
-				if micro != 0 {
-					micro10000 := micro / 10000
-					micro100 := micro / 100 % 100
-					micro1 := micro % 100
-					buf = append(buf, []byte{
-						'.',
-						digits10[micro10000], digits01[micro10000],
-						digits10[micro100], digits01[micro100],
-						digits10[micro1], digits01[micro1],
-					}...)
-				}
-				buf = append(buf, '\'')
-			}
-		case []byte:
-			if v == nil {
-				buf = append(buf, "NULL"...)
-			} else {
-				buf = append(buf, "_binary'"...)
-				if mc.status&statusNoBackslashEscapes == 0 {
-					buf = escapeBytesBackslash(buf, v)
-				} else {
-					buf = escapeBytesQuotes(buf, v)
-				}
-				buf = append(buf, '\'')
-			}
-		case string:
-			buf = append(buf, '\'')
-			if mc.status&statusNoBackslashEscapes == 0 {
-				buf = escapeStringBackslash(buf, v)
-			} else {
-				buf = escapeStringQuotes(buf, v)
-			}
-			buf = append(buf, '\'')
-		default:
-			return "", driver.ErrSkip
-		}
-
-		if len(buf)+4 > mc.maxAllowedPacket {
-			return "", driver.ErrSkip
-		}
-	}
-	if argPos != len(args) {
-		return "", driver.ErrSkip
-	}
-	return string(buf), nil
-}
-
-func (mc *mysqlConn) Exec(query string, args []driver.Value) (driver.Result, error) {
-	if mc.closed.IsSet() {
-		errLog.Print(ErrInvalidConn)
-		return nil, driver.ErrBadConn
-	}
-	if len(args) != 0 {
-		if !mc.cfg.InterpolateParams {
-			return nil, driver.ErrSkip
-		}
-		// try to interpolate the parameters to save extra roundtrips for preparing and closing a statement
-		prepared, err := mc.interpolateParams(query, args)
-		if err != nil {
-			return nil, err
-		}
-		query = prepared
-	}
-	mc.affectedRows = 0
-	mc.insertID = 0
-
-	err := mc.exec(query)
-	if err == nil {
-		return &mysqlResult{
-			affectedRows: int64(mc.affectedRows),
-			insertID:     int64(mc.insertID),
-		}, err
-	}
-	return nil, mc.markBadConn(err)
-}
-
 // Internal function to execute commands
 func (mc *mysqlConn) exec(query string) error {
 	// Send command
diff --git a/mysql/driver/connection_extended.go b/mysql/driver/connection_extended.go
index a5064a6..62c690b 100644
--- a/mysql/driver/connection_extended.go
+++ b/mysql/driver/connection_extended.go
@@ -5,6 +5,11 @@ import (
 	"time"
 )
 
+// ExtendedConn provides access to internal packet functions.
+type ExtendedConn struct {
+	*mysqlConn
+}
+
 // NewExtendedConnection creates a new connection extended with packet access
 // methods.
 func NewExtendedConnection(dsn string) (*ExtendedConn, error) {
@@ -15,17 +20,9 @@ func NewExtendedConnection(dsn string) (*ExtendedConn, error) {
 	return &ExtendedConn{conn}, nil
 }
 
-// ExtendedConn provides access to internal packet functions.
-type ExtendedConn struct {
-	*mysqlConn
-}
-
-// Close the connection.
-func (c *ExtendedConn) Close() error {
-	// Reset buffer length parameter
-	// If it's not zero bad stuff happens
-	c.buf.length = 0
-	return c.mysqlConn.Close()
+// Exec executes a query.
+func (c *ExtendedConn) Exec(query string) error {
+	return c.exec(query)
 }
 
 // ReadPacket reads a packet from a given connection. If given context has a
@@ -65,3 +62,11 @@ func (c *ExtendedConn) HandleErrorPacket(data []byte) error {
 func (c *ExtendedConn) ResetSequence() {
 	c.sequence = 0
 }
+
+// Close the connection.
+func (c *ExtendedConn) Close() error {
+	// Reset buffer length parameter
+	// If it's not zero bad stuff happens
+	c.buf.length = 0
+	return c.mysqlConn.Close()
+}
diff --git a/mysql/slave/slave_conn.go b/mysql/slave/slave_conn.go
index c06ba65..3ba946a 100644
--- a/mysql/slave/slave_conn.go
+++ b/mysql/slave/slave_conn.go
@@ -121,8 +121,7 @@ func (c *Conn) DisableChecksum() error {
 
 // SetVar assigns a new value to the given variable.
 func (c *Conn) SetVar(name, val string) error {
-	_, err := c.conn.Exec(fmt.Sprintf("SET %s=%q", name, val), nil)
-	return err
+	return c.conn.Exec(fmt.Sprintf("SET %s=%q", name, val))
 }
 
 // Close the connection.