diff --git a/chainable_api.go b/chainable_api.go
index 75e0fa2a..95d5975c 100644
--- a/chainable_api.go
+++ b/chainable_api.go
@@ -1,5 +1,7 @@
 package gorm
 
+import "github.com/jinzhu/gorm/clause"
+
 // Model specify the model you would like to run db operations
 //    // update all users's name to `hello`
 //    db.Model(&User{}).Update("name", "hello")
@@ -11,6 +13,27 @@ func (db *DB) Model(value interface{}) (tx *DB) {
 	return
 }
 
+// Clauses Add clauses
+func (db *DB) Clauses(conds ...clause.Expression) (tx *DB) {
+	tx = db.getInstance()
+	var whereConds []interface{}
+
+	for _, cond := range conds {
+		if c, ok := cond.(clause.Interface); ok {
+			tx.Statement.AddClause(c)
+		} else {
+			whereConds = append(whereConds, cond)
+		}
+	}
+
+	if len(whereConds) > 0 {
+		tx.Statement.AddClause(clause.Where{
+			AndConditions: tx.Statement.BuildCondtion(whereConds[0], whereConds[1:]...),
+		})
+	}
+	return
+}
+
 // Table specify the table you would like to run db operations
 func (db *DB) Table(name string) (tx *DB) {
 	tx = db.getInstance()
@@ -32,18 +55,25 @@ func (db *DB) Omit(columns ...string) (tx *DB) {
 
 func (db *DB) Where(query interface{}, args ...interface{}) (tx *DB) {
 	tx = db.getInstance()
+	tx.Statement.AddClause(clause.Where{AndConditions: tx.Statement.BuildCondtion(query, args...)})
 	return
 }
 
 // Not add NOT condition
 func (db *DB) Not(query interface{}, args ...interface{}) (tx *DB) {
 	tx = db.getInstance()
+	tx.Statement.AddClause(clause.Where{
+		AndConditions: []clause.Expression{clause.NotConditions(tx.Statement.BuildCondtion(query, args...))},
+	})
 	return
 }
 
 // Or add OR conditions
 func (db *DB) Or(query interface{}, args ...interface{}) (tx *DB) {
 	tx = db.getInstance()
+	tx.Statement.AddClause(clause.Where{
+		ORConditions: []clause.ORConditions{tx.Statement.BuildCondtion(query, args...)},
+	})
 	return
 }
 
@@ -98,20 +128,13 @@ func (db *DB) Offset(offset int64) (tx *DB) {
 //     }
 //
 //     db.Scopes(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Find(&orders)
-// Refer https://jinzhu.github.io/gorm/crud.html#scopes
-func (db *DB) Scopes(funcs ...func(*DB) *DB) (tx *DB) {
+func (db *DB) Scopes(funcs ...func(*DB) *DB) *DB {
 	for _, f := range funcs {
 		db = f(db)
 	}
 	return db
 }
 
-//Preloads only preloads relations, don`t touch out
-func (db *DB) Preloads(out interface{}) (tx *DB) {
-	tx = db.getInstance()
-	return
-}
-
 // Preload preload associations with given conditions
 //    db.Preload("Orders", "state NOT IN (?)", "cancelled").Find(&users)
 func (db *DB) Preload(column string, conditions ...interface{}) (tx *DB) {
diff --git a/clause/clause.go b/clause/clause.go
index 1afb120e..b0507f44 100644
--- a/clause/clause.go
+++ b/clause/clause.go
@@ -1,31 +1,131 @@
 package clause
 
-// Builder builder interface
-type BuilderInterface interface {
-	Write(sql ...string) error
-	WriteQuoted(field interface{}) error
-	AddVar(vars ...interface{}) string
-	Quote(field interface{}) string
+// Clause
+type Clause struct {
+	Name                 string // WHERE
+	Priority             float64
+	BeforeExpressions    []Expression
+	AfterNameExpressions []Expression
+	AfterExpressions     []Expression
+	Expression           Expression
+	Builder              ClauseBuilder
+}
+
+// ClauseBuilder clause builder, allows to custmize how to build clause
+type ClauseBuilder interface {
+	Build(Clause, Builder)
+}
+
+// Build build clause
+func (c Clause) Build(builder Builder) {
+	if c.Builder != nil {
+		c.Builder.Build(c, builder)
+	} else {
+		builders := c.BeforeExpressions
+		if c.Name != "" {
+			builders = append(builders, Expr{c.Name})
+		}
+
+		builders = append(builders, c.AfterNameExpressions...)
+		if c.Expression != nil {
+			builders = append(builders, c.Expression)
+		}
+
+		for idx, expr := range append(builders, c.AfterExpressions...) {
+			if idx != 0 {
+				builder.WriteByte(' ')
+			}
+			expr.Build(builder)
+		}
+	}
 }
 
 // Interface clause interface
 type Interface interface {
 	Name() string
-	Builder
+	Build(Builder)
+	MergeExpression(Expression)
 }
 
-// Builder condition builder
-type Builder interface {
-	Build(builder BuilderInterface)
+type OverrideNameInterface interface {
+	OverrideName() string
 }
 
-// NegationBuilder negation condition builder
-type NegationBuilder interface {
-	NegationBuild(builder BuilderInterface)
-}
+////////////////////////////////////////////////////////////////////////////////
+// Predefined Clauses
+////////////////////////////////////////////////////////////////////////////////
 
 // Where where clause
 type Where struct {
+	AndConditions AddConditions
+	ORConditions  []ORConditions
+	Builders      []Expression
+}
+
+func (where Where) Name() string {
+	return "WHERE"
+}
+
+func (where Where) Build(builder Builder) {
+	var withConditions bool
+
+	if len(where.AndConditions) > 0 {
+		withConditions = true
+		where.AndConditions.Build(builder)
+	}
+
+	if len(where.Builders) > 0 {
+		for _, b := range where.Builders {
+			if withConditions {
+				builder.Write(" AND ")
+			}
+			withConditions = true
+			b.Build(builder)
+		}
+	}
+
+	var singleOrConditions []ORConditions
+	for _, or := range where.ORConditions {
+		if len(or) == 1 {
+			if withConditions {
+				builder.Write(" OR ")
+				or.Build(builder)
+			} else {
+				singleOrConditions = append(singleOrConditions, or)
+			}
+		} else {
+			withConditions = true
+			builder.Write(" AND (")
+			or.Build(builder)
+			builder.WriteByte(')')
+		}
+	}
+
+	for _, or := range singleOrConditions {
+		if withConditions {
+			builder.Write(" AND ")
+			or.Build(builder)
+		} else {
+			withConditions = true
+			or.Build(builder)
+		}
+	}
+
+	if !withConditions {
+		builder.Write(" FALSE")
+	}
+
+	return
+}
+
+func (where Where) MergeExpression(expr Expression) {
+	if w, ok := expr.(Where); ok {
+		where.AndConditions = append(where.AndConditions, w.AndConditions...)
+		where.ORConditions = append(where.ORConditions, w.ORConditions...)
+		where.Builders = append(where.Builders, w.Builders...)
+	} else {
+		where.Builders = append(where.Builders, expr)
+	}
 }
 
 // Select select attrs when querying, updating, creating
diff --git a/clause/expr.go b/clause/expr.go
deleted file mode 100644
index 94edb702..00000000
--- a/clause/expr.go
+++ /dev/null
@@ -1,19 +0,0 @@
-package clause
-
-type ExprInterface interface {
-}
-
-type Expr struct {
-}
-
-type Average struct {
-}
-
-type Minimum struct {
-}
-
-type Maximum struct {
-}
-
-type Sum struct {
-}
diff --git a/clause/expression.go b/clause/expression.go
new file mode 100644
index 00000000..17313d43
--- /dev/null
+++ b/clause/expression.go
@@ -0,0 +1,30 @@
+package clause
+
+// Expression expression interface
+type Expression interface {
+	Build(builder Builder)
+}
+
+// NegationExpressionBuilder negation expression builder
+type NegationExpressionBuilder interface {
+	NegationBuild(builder Builder)
+}
+
+// Builder builder interface
+type Builder interface {
+	WriteByte(byte) error
+	Write(sql ...string) error
+	WriteQuoted(field interface{}) error
+	AddVar(vars ...interface{}) string
+	Quote(field interface{}) string
+}
+
+// Expr raw expression
+type Expr struct {
+	Value string
+}
+
+// Build build raw expression
+func (expr Expr) Build(builder Builder) {
+	builder.Write(expr.Value)
+}
diff --git a/clause/operators.go b/clause/query.go
similarity index 66%
rename from clause/operators.go
rename to clause/query.go
index a6bdb4aa..949678d9 100644
--- a/clause/operators.go
+++ b/clause/query.go
@@ -2,10 +2,13 @@ package clause
 
 import "strings"
 
-type Condition Builder
-type AddConditions []Condition
+////////////////////////////////////////////////////////////////////////////////
+// Query Expressions
+////////////////////////////////////////////////////////////////////////////////
 
-func (cs AddConditions) Build(builder BuilderInterface) {
+type AddConditions []Expression
+
+func (cs AddConditions) Build(builder Builder) {
 	for idx, c := range cs {
 		if idx > 0 {
 			builder.Write(" AND ")
@@ -14,9 +17,9 @@ func (cs AddConditions) Build(builder BuilderInterface) {
 	}
 }
 
-type ORConditions []Condition
+type ORConditions []Expression
 
-func (cs ORConditions) Build(builder BuilderInterface) {
+func (cs ORConditions) Build(builder Builder) {
 	for idx, c := range cs {
 		if idx > 0 {
 			builder.Write(" OR ")
@@ -25,15 +28,15 @@ func (cs ORConditions) Build(builder BuilderInterface) {
 	}
 }
 
-type NotConditions []Condition
+type NotConditions []Expression
 
-func (cs NotConditions) Build(builder BuilderInterface) {
+func (cs NotConditions) Build(builder Builder) {
 	for idx, c := range cs {
 		if idx > 0 {
 			builder.Write(" AND ")
 		}
 
-		if negationBuilder, ok := c.(NegationBuilder); ok {
+		if negationBuilder, ok := c.(NegationExpressionBuilder); ok {
 			negationBuilder.NegationBuild(builder)
 		} else {
 			builder.Write(" NOT ")
@@ -42,15 +45,15 @@ func (cs NotConditions) Build(builder BuilderInterface) {
 	}
 }
 
-// Raw raw sql for where
-type Raw struct {
+// String raw sql for where
+type String struct {
 	SQL    string
 	Values []interface{}
 }
 
-func (raw Raw) Build(builder BuilderInterface) {
-	sql := raw.SQL
-	for _, v := range raw.Values {
+func (str String) Build(builder Builder) {
+	sql := str.SQL
+	for _, v := range str.Values {
 		sql = strings.Replace(sql, " ? ", " "+builder.AddVar(v)+" ", 1)
 	}
 	builder.Write(sql)
@@ -62,7 +65,7 @@ type IN struct {
 	Values []interface{}
 }
 
-func (in IN) Build(builder BuilderInterface) {
+func (in IN) Build(builder Builder) {
 	builder.WriteQuoted(in.Column)
 
 	switch len(in.Values) {
@@ -75,7 +78,7 @@ func (in IN) Build(builder BuilderInterface) {
 	}
 }
 
-func (in IN) NegationBuild(builder BuilderInterface) {
+func (in IN) NegationBuild(builder Builder) {
 	switch len(in.Values) {
 	case 0:
 	case 1:
@@ -91,7 +94,7 @@ type Eq struct {
 	Value  interface{}
 }
 
-func (eq Eq) Build(builder BuilderInterface) {
+func (eq Eq) Build(builder Builder) {
 	builder.WriteQuoted(eq.Column)
 
 	if eq.Value == nil {
@@ -101,7 +104,7 @@ func (eq Eq) Build(builder BuilderInterface) {
 	}
 }
 
-func (eq Eq) NegationBuild(builder BuilderInterface) {
+func (eq Eq) NegationBuild(builder Builder) {
 	Neq{eq.Column, eq.Value}.Build(builder)
 }
 
@@ -111,7 +114,7 @@ type Neq struct {
 	Value  interface{}
 }
 
-func (neq Neq) Build(builder BuilderInterface) {
+func (neq Neq) Build(builder Builder) {
 	builder.WriteQuoted(neq.Column)
 
 	if neq.Value == nil {
@@ -121,7 +124,7 @@ func (neq Neq) Build(builder BuilderInterface) {
 	}
 }
 
-func (neq Neq) NegationBuild(builder BuilderInterface) {
+func (neq Neq) NegationBuild(builder Builder) {
 	Eq{neq.Column, neq.Value}.Build(builder)
 }
 
@@ -131,12 +134,12 @@ type Gt struct {
 	Value  interface{}
 }
 
-func (gt Gt) Build(builder BuilderInterface) {
+func (gt Gt) Build(builder Builder) {
 	builder.WriteQuoted(gt.Column)
 	builder.Write(" > ", builder.AddVar(gt.Value))
 }
 
-func (gt Gt) NegationBuild(builder BuilderInterface) {
+func (gt Gt) NegationBuild(builder Builder) {
 	Lte{gt.Column, gt.Value}.Build(builder)
 }
 
@@ -146,12 +149,12 @@ type Gte struct {
 	Value  interface{}
 }
 
-func (gte Gte) Build(builder BuilderInterface) {
+func (gte Gte) Build(builder Builder) {
 	builder.WriteQuoted(gte.Column)
 	builder.Write(" >= ", builder.AddVar(gte.Value))
 }
 
-func (gte Gte) NegationBuild(builder BuilderInterface) {
+func (gte Gte) NegationBuild(builder Builder) {
 	Lt{gte.Column, gte.Value}.Build(builder)
 }
 
@@ -161,12 +164,12 @@ type Lt struct {
 	Value  interface{}
 }
 
-func (lt Lt) Build(builder BuilderInterface) {
+func (lt Lt) Build(builder Builder) {
 	builder.WriteQuoted(lt.Column)
 	builder.Write(" < ", builder.AddVar(lt.Value))
 }
 
-func (lt Lt) NegationBuild(builder BuilderInterface) {
+func (lt Lt) NegationBuild(builder Builder) {
 	Gte{lt.Column, lt.Value}.Build(builder)
 }
 
@@ -176,12 +179,12 @@ type Lte struct {
 	Value  interface{}
 }
 
-func (lte Lte) Build(builder BuilderInterface) {
+func (lte Lte) Build(builder Builder) {
 	builder.WriteQuoted(lte.Column)
 	builder.Write(" <= ", builder.AddVar(lte.Value))
 }
 
-func (lte Lte) NegationBuild(builder BuilderInterface) {
+func (lte Lte) NegationBuild(builder Builder) {
 	Gt{lte.Column, lte.Value}.Build(builder)
 }
 
@@ -191,12 +194,12 @@ type Like struct {
 	Value  interface{}
 }
 
-func (like Like) Build(builder BuilderInterface) {
+func (like Like) Build(builder Builder) {
 	builder.WriteQuoted(like.Column)
 	builder.Write(" LIKE ", builder.AddVar(like.Value))
 }
 
-func (like Like) NegationBuild(builder BuilderInterface) {
+func (like Like) NegationBuild(builder Builder) {
 	builder.WriteQuoted(like.Column)
 	builder.Write(" NOT LIKE ", builder.AddVar(like.Value))
 }
@@ -204,11 +207,11 @@ func (like Like) NegationBuild(builder BuilderInterface) {
 // Map
 type Map map[interface{}]interface{}
 
-func (m Map) Build(builder BuilderInterface) {
+func (m Map) Build(builder Builder) {
 	// TODO
 }
 
-func (m Map) NegationBuild(builder BuilderInterface) {
+func (m Map) NegationBuild(builder Builder) {
 	// TODO
 }
 
@@ -219,13 +222,13 @@ type Attrs struct {
 	Omit   []string
 }
 
-func (attrs Attrs) Build(builder BuilderInterface) {
+func (attrs Attrs) Build(builder Builder) {
 	// TODO
 	// builder.WriteQuoted(like.Column)
 	// builder.Write(" LIKE ", builder.AddVar(like.Value))
 }
 
-func (attrs Attrs) NegationBuild(builder BuilderInterface) {
+func (attrs Attrs) NegationBuild(builder Builder) {
 	// TODO
 }
 
@@ -234,7 +237,7 @@ type ID struct {
 	Value []interface{}
 }
 
-func (id ID) Build(builder BuilderInterface) {
+func (id ID) Build(builder Builder) {
 	if len(id.Value) == 1 {
 	}
 	// TODO
@@ -242,6 +245,6 @@ func (id ID) Build(builder BuilderInterface) {
 	// builder.Write(" LIKE ", builder.AddVar(like.Value))
 }
 
-func (id ID) NegationBuild(builder BuilderInterface) {
+func (id ID) NegationBuild(builder Builder) {
 	// TODO
 }
diff --git a/errors.go b/errors.go
new file mode 100644
index 00000000..c66408be
--- /dev/null
+++ b/errors.go
@@ -0,0 +1,22 @@
+package gorm
+
+import "errors"
+
+var (
+	// ErrRecordNotFound record not found error
+	ErrRecordNotFound = errors.New("record not found")
+	// ErrInvalidSQL invalid SQL error, happens when you passed invalid SQL
+	ErrInvalidSQL = errors.New("invalid SQL")
+	// ErrInvalidTransaction invalid transaction when you are trying to `Commit` or `Rollback`
+	ErrInvalidTransaction = errors.New("no valid transaction")
+	// ErrUnaddressable unaddressable value
+	ErrUnaddressable = errors.New("using unaddressable value")
+)
+
+type Error struct {
+	Err error
+}
+
+func (e Error) Unwrap() error {
+	return e.Err
+}
diff --git a/finisher_api.go b/finisher_api.go
index 687843e3..2668e1fe 100644
--- a/finisher_api.go
+++ b/finisher_api.go
@@ -33,8 +33,6 @@ func (db *DB) Find(out interface{}, where ...interface{}) (tx *DB) {
 	return
 }
 
-// Scan scan value to a struct
-
 func (db *DB) Row() *sql.Row {
 	// TODO
 	return nil
@@ -45,6 +43,7 @@ func (db *DB) Rows() (*sql.Rows, error) {
 	return nil, nil
 }
 
+// Scan scan value to a struct
 func (db *DB) Scan(dest interface{}) (tx *DB) {
 	tx = db.getInstance()
 	return
@@ -88,12 +87,12 @@ func (db *DB) UpdateColumns(values interface{}) (tx *DB) {
 	return
 }
 
-func (db *DB) FirstOrCreate(out interface{}, where ...interface{}) (tx *DB) {
+func (db *DB) FirstOrInit(out interface{}, where ...interface{}) (tx *DB) {
 	tx = db.getInstance()
 	return
 }
 
-func (db *DB) FirstOrInit(out interface{}, where ...interface{}) (tx *DB) {
+func (db *DB) FirstOrCreate(out interface{}, where ...interface{}) (tx *DB) {
 	tx = db.getInstance()
 	return
 }
@@ -109,6 +108,16 @@ func (db *DB) Related(value interface{}, foreignKeys ...string) (tx *DB) {
 	return
 }
 
+//Preloads only preloads relations, don`t touch out
+func (db *DB) Preloads(out interface{}) (tx *DB) {
+	tx = db.getInstance()
+	return
+}
+
+func (db *DB) Association(column string) *Association {
+	return nil
+}
+
 func (db *DB) Transaction(fc func(tx *DB) error, opts ...*sql.TxOptions) (err error) {
 	panicked := true
 	tx := db.Begin(opts...)
@@ -148,7 +157,3 @@ func (db *DB) Exec(sql string, values ...interface{}) (tx *DB) {
 	tx = db.getInstance()
 	return
 }
-
-func (db *DB) Association(column string) *Association {
-	return nil
-}
diff --git a/gorm.go b/gorm.go
index 86d5af9a..838f2862 100644
--- a/gorm.go
+++ b/gorm.go
@@ -25,44 +25,72 @@ type Config struct {
 	NowFunc func() time.Time
 }
 
-// Model a basic GoLang struct which includes the following fields: ID, CreatedAt, UpdatedAt, DeletedAt
-// It may be embeded into your model or you may build your own model without it
-//    type User struct {
-//      gorm.Model
-//    }
-type Model struct {
-	ID        uint `gorm:"primary_key"`
-	CreatedAt time.Time
-	UpdatedAt time.Time
-	DeletedAt *time.Time `gorm:"index"`
-}
-
 // Dialector GORM database dialector
 type Dialector interface {
 	Migrator() Migrator
 	BindVar(stmt Statement, v interface{}) string
 }
 
-// Result
-type Result struct {
-	Error        error
-	RowsAffected int64
-	Statement    *Statement
-}
-
 // DB GORM DB definition
 type DB struct {
 	*Config
 	Dialector
-	Result
+	Instance
+	clone bool
+}
+
+// Session session config when create new session
+type Session struct {
 	Context context.Context
+	Logger  logger.Interface
+	NowFunc func() time.Time
+}
+
+// Open initialize db session based on dialector
+func Open(dialector Dialector, config *Config) (db *DB, err error) {
+	return &DB{
+		Config:    config,
+		Dialector: dialector,
+		clone:     true,
+	}, nil
+}
+
+// Session create new db session
+func (db *DB) Session(config *Session) *DB {
+	var (
+		tx       = db.getInstance()
+		txConfig = *tx.Config
+	)
+
+	if config.Context != nil {
+		tx.Context = config.Context
+	}
+
+	if config.Logger != nil {
+		txConfig.Logger = config.Logger
+	}
+
+	if config.NowFunc != nil {
+		txConfig.NowFunc = config.NowFunc
+	}
+
+	tx.Config = &txConfig
+	tx.clone = true
+	return tx
 }
 
 // WithContext change current instance db's context to ctx
 func (db *DB) WithContext(ctx context.Context) *DB {
-	tx := db.getInstance()
-	tx.Context = ctx
-	return tx
+	return db.Session(&Session{Context: ctx})
+}
+
+// Debug start debug mode
+func (db *DB) Debug() (tx *DB) {
+	return db.Session(&Session{Logger: db.Logger.LogMode(logger.Info)})
+}
+
+func (db *DB) Close() error {
+	return nil
 }
 
 // Set store value with key into current db instance's context
@@ -80,35 +108,22 @@ func (db *DB) Get(key string) (interface{}, bool) {
 	return nil, false
 }
 
-func (db *DB) Close() *DB {
-	// TODO
-	return db
-}
-
 func (db *DB) getInstance() *DB {
-	// db.Result.Statement == nil means root DB
-	if db.Result.Statement == nil {
+	if db.clone {
+		ctx := db.Instance.Context
+		if ctx == nil {
+			ctx = context.Background()
+		}
+
 		return &DB{
 			Config:    db.Config,
 			Dialector: db.Dialector,
-			Context:   context.Background(),
-			Result: Result{
-				Statement: &Statement{DB: db, Clauses: map[string][]clause.Condition{}},
+			Instance: Instance{
+				Context:   ctx,
+				Statement: &Statement{DB: db, Clauses: map[string]clause.Clause{}},
 			},
 		}
 	}
 
 	return db
 }
-
-// Debug start debug mode
-func (db *DB) Debug() (tx *DB) {
-	tx = db.getInstance()
-	return
-}
-
-// Session start session mode
-func (db *DB) Session() (tx *DB) {
-	tx = db.getInstance()
-	return
-}
diff --git a/logger/logger.go b/logger/logger.go
index 87b71013..389a6763 100644
--- a/logger/logger.go
+++ b/logger/logger.go
@@ -1,5 +1,14 @@
 package logger
 
+type LogLevel int
+
+const (
+	Info LogLevel = iota + 1
+	Warn
+	Error
+)
+
 // Interface logger interface
 type Interface interface {
+	LogMode(LogLevel) Interface
 }
diff --git a/model.go b/model.go
new file mode 100644
index 00000000..118d8f14
--- /dev/null
+++ b/model.go
@@ -0,0 +1,15 @@
+package gorm
+
+import "time"
+
+// Model a basic GoLang struct which includes the following fields: ID, CreatedAt, UpdatedAt, DeletedAt
+// It may be embeded into your model or you may build your own model without it
+//    type User struct {
+//      gorm.Model
+//    }
+type Model struct {
+	ID        uint `gorm:"primary_key"`
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	DeletedAt *time.Time `gorm:"index"`
+}
diff --git a/statement.go b/statement.go
index 5dab59b3..30d45b98 100644
--- a/statement.go
+++ b/statement.go
@@ -1,7 +1,6 @@
 package gorm
 
 import (
-	"bytes"
 	"context"
 	"database/sql"
 	"database/sql/driver"
@@ -13,25 +12,43 @@ import (
 	"github.com/jinzhu/gorm/clause"
 )
 
-// Statement statement
-type Statement struct {
-	Model    interface{}
-	Dest     interface{}
-	Table    string
-	Clauses  map[string][]clause.Condition
-	Settings sync.Map
-	Context  context.Context
-	DB       *DB
-	StatementBuilder
+// Instance db instance
+type Instance struct {
+	Error        error
+	RowsAffected int64
+	Context      context.Context
+	Statement    *Statement
 }
 
-// StatementBuilder statement builder
-type StatementBuilder struct {
-	SQL       bytes.Buffer
+// AddError add error to instance
+func (inst Instance) AddError(err error) {
+	if inst.Error == nil {
+		inst.Error = err
+	} else {
+		inst.Error = fmt.Errorf("%v; %w", inst.Error, err)
+	}
+}
+
+// Statement statement
+type Statement struct {
+	Table    string
+	Model    interface{}
+	Dest     interface{}
+	Clauses  map[string]clause.Clause
+	Settings sync.Map
+	DB       *DB
+
+	// SQL Builder
+	SQL       strings.Builder
 	Vars      []interface{}
 	NamedVars []sql.NamedArg
 }
 
+// StatementOptimizer statement optimizer interface
+type StatementOptimizer interface {
+	OptimizeStatement(Statement)
+}
+
 // Write write string
 func (stmt Statement) Write(sql ...string) (err error) {
 	for _, s := range sql {
@@ -40,12 +57,23 @@ func (stmt Statement) Write(sql ...string) (err error) {
 	return
 }
 
+// Write write string
+func (stmt Statement) WriteByte(c byte) (err error) {
+	return stmt.SQL.WriteByte(c)
+}
+
 // WriteQuoted write quoted field
 func (stmt Statement) WriteQuoted(field interface{}) (err error) {
 	_, err = stmt.SQL.WriteString(stmt.Quote(field))
 	return
 }
 
+// Quote returns quoted value
+func (stmt Statement) Quote(field interface{}) (str string) {
+	// FIXME
+	return fmt.Sprint(field)
+}
+
 // Write write string
 func (stmt Statement) AddVar(vars ...interface{}) string {
 	var placeholders strings.Builder
@@ -73,23 +101,34 @@ func (stmt Statement) AddVar(vars ...interface{}) string {
 	return placeholders.String()
 }
 
-// Quote returns quoted value
-func (stmt Statement) Quote(field interface{}) (str string) {
-	return fmt.Sprint(field)
-}
-
 // AddClause add clause
-func (s Statement) AddClause(clause clause.Interface) {
-	s.Clauses[clause.Name()] = append(s.Clauses[clause.Name()], clause)
+func (stmt Statement) AddClause(v clause.Interface) {
+	if optimizer, ok := v.(StatementOptimizer); ok {
+		optimizer.OptimizeStatement(stmt)
+	}
+
+	c, _ := stmt.Clauses[v.Name()]
+	if namer, ok := v.(clause.OverrideNameInterface); ok {
+		c.Name = namer.OverrideName()
+	} else {
+		c.Name = v.Name()
+	}
+
+	if c.Expression != nil {
+		v.MergeExpression(c.Expression)
+	}
+
+	c.Expression = v
+	stmt.Clauses[v.Name()] = c
 }
 
-// BuildCondtions build conditions
-func (s Statement) BuildCondtions(query interface{}, args ...interface{}) (conditions []clause.Condition) {
+// BuildCondtion build condition
+func (stmt Statement) BuildCondtion(query interface{}, args ...interface{}) (conditions []clause.Expression) {
 	if sql, ok := query.(string); ok {
 		if i, err := strconv.Atoi(sql); err != nil {
 			query = i
 		} else if len(args) == 0 || (len(args) > 0 && strings.Contains(sql, "?")) || strings.Contains(sql, "@") {
-			return []clause.Condition{clause.Raw{SQL: sql, Values: args}}
+			return []clause.Expression{clause.String{SQL: sql, Values: args}}
 		}
 	}
 
@@ -100,12 +139,12 @@ func (s Statement) BuildCondtions(query interface{}, args ...interface{}) (condi
 		}
 
 		switch v := arg.(type) {
-		case clause.Builder:
+		case clause.Expression:
 			conditions = append(conditions, v)
 		case *DB:
 			if v.Statement == nil {
 				if cs, ok := v.Statement.Clauses["WHERE"]; ok {
-					conditions = append(conditions, cs...)
+					conditions = append(conditions, cs.Expression)
 				}
 			}
 		case map[interface{}]interface{}:
@@ -135,8 +174,22 @@ func (s Statement) BuildCondtions(query interface{}, args ...interface{}) (condi
 	if len(conditions) == 0 {
 		conditions = append(conditions, clause.ID{Value: args})
 	}
+
 	return conditions
 }
 
-func (s Statement) AddError(err error) {
+// Build build sql with clauses names
+func (stmt Statement) Build(clauses ...string) {
+	var includeSpace bool
+
+	for _, name := range clauses {
+		if c, ok := stmt.Clauses[name]; ok {
+			if includeSpace {
+				stmt.WriteByte(' ')
+			}
+
+			includeSpace = true
+			c.Build(stmt)
+		}
+	}
 }