diff --git a/README.md b/README.md
index 28b8d08b..96cbc91b 100644
--- a/README.md
+++ b/README.md
@@ -6,167 +6,306 @@ Yet Another ORM library for Go, aims for developer friendly
 
 * CURD
 * Chainable API
+* Embedded structs support
 * Before/After Create/Save/Update/Delete Callbacks
-* Order/Select/Limit/Offset Support
 * Update, Updates Like Rails's update_attribute, update_attributes
 * FirstOrInit, FirstOrCreate Like Rails's first_or_initialize, first_or_create
-* Dynamically set table name when search, update, delete...
+* Order/Select/Limit/Offset Support
 * Automatically CreatedAt, UpdatedAt
 * Soft Delete
-* Create table from struct
+* Create/Drop table from struct
+* Dynamically set table name when search, create, update, delete...
 * Prevent SQL Injection
 * Goroutines friendly
 * Database Pool
+* Convention Over Configuration (CoC)
 
 ## Basic Usage
 
-```go
-db, _ = Open("postgres", "user=gorm dbname=gorm sslmode=disable")
+## Opening a Database
 
-type User struct {
-  Id        int64
-  Age       int64
-  Birthday  time.Time
-  Name      string
-  CreatedAt time.Time
-  UpdatedAt time.Time
+```go
+db, err = Open("postgres", "user=gorm dbname=gorm sslmode=disable")
+
+// Gorm is goroutines friendly, so you can create a global variable to keep the connection and use it everywhere
+
+var DB gorm.DB
+
+func init() {
+    DB, err = gorm.Open("postgres", "user=gorm dbname=gorm sslmode=disable")
+    if err != nil {
+        panic(fmt.Sprintf("Got error when connect database, the error is '%v'", err))
+    }
 }
 
-// Set database pool
-db.SetPool(10)
+// Set the maximum idle database connections
+db.SetPool(100)
+```
 
-// Create
-user = User{Name: "jinzhu", Age: 18, Birthday: time.Now()}
+## Conventions
+
+```go
+type User struct {              // TableName: `users`, gorm will pluralize struct name as table name
+	Id                int64     // Id: Database Primary key
+	Birthday          time.Time // Time
+	Age               int64
+	Name              string
+	CreatedAt         time.Time // CreatedAt: Time of record is created, will be insert automatically
+	UpdatedAt         time.Time // UpdatedAt: Time of record is updated, will be updated automatically
+	DeletedAt         time.Time // DeletedAt: Time of record is deleted, refer Soft Delete for more
+	Email             []Email   // Embedded structs
+	BillingAddress    Address   // Embedded struct
+	BillingAddressId  int64     // Embedded struct's foreign key
+	ShippingAddress   Address   // Embedded struct
+	ShippingAddressId int64     // Embedded struct's foreign key
+}
+
+type Email struct {    // TableName: `emails`
+	Id         int64
+	UserId     int64   // Foreign key for above embedded structs
+	Email      string
+	Subscribed bool
+}
+
+type Address struct {  // TableName: `addresses`
+	Id       int64
+	Address1 string
+	Address2 string
+	Post     string
+}
+```
+
+## Struct & Database Mapping
+
+```go
+// Create table from struct
+db.CreateTable(User{})
+
+// Drop table
+db.DropTable(User{})
+```
+
+## Create
+
+```go
+user := User{Name: "jinzhu", Age: 18, Birthday: time.Now()}
 db.Save(&user)
+```
 
-// Update
+## Update
+
+```go
 user.Name = "jinzhu 2"
 db.Save(&user)
+```
 
-// Delete
+## Delete
+
+```go
 db.Delete(&user)
+```
 
-// Get First matched record
+## Query
+
+```go
+// Get the first record
+db.First(&user)
+//// SELECT * FROM USERS LIMIT 1;
+
+// Get All records
+db.Find(&users)
+//// SELECT * FROM USERS;
+
+// Using a Primary Key
+db.First(&user, 10)
+//// SELECT * FROM USERS WHERE id = 10;
+```
+
+### Where (SQL like condition)
+
+```go
+// Get the first matched record
 db.Where("name = ?", "jinzhu").First(&user)
+//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;
 
-// Get All matched records
+// Get all matched records
 db.Where("name = ?", "jinzhu").Find(&users)
+//// SELECT * FROM users WHERE name = 'jinzhu';
 
-// Advanced Where Usage
 db.Where("name <> ?", "jinzhu").Find(&users)
-//// users -> select * from users name <> 'jinzhu';
-db.Where(20).First(&user)
-//// users -> select * from users where id = 20;
-db.Where([]int64{20, 21, 22}).Find(&user)
-//// users -> select * from users where id in (20, 21, 22);
-db.Where("name = ? and age >= ?", "jinzhu", "22").Find(&users)
-//// users -> select * from users name = 'jinzhu' and age >= 22;
+//// SELECT * FROM users WHERE name <> 'jinzhu';
+
+// IN
 db.Where("name in (?)", []string["jinzhu", "jinzhu 2"]).Find(&users)
-//// users -> select * from users name in ('jinzhu', 'jinzhu 2');
+//// SELECT * FROM users WHERE name IN ('jinzhu', 'jinzhu 2');
+
+// IN For Primary Key
+db.Where([]int64{20, 21, 22}).Find(&users)
+//// SELECT * FROM users WHERE id IN (20, 21, 22);
+
+// LIKE
 db.Where("name LIKE ?", "%jin%").Find(&users)
-//// users -> select * from users name LIKE "%jinzhu%";
+//// SELECT * FROM users WHERE name LIKE "%jin%";
+
+// Multiple Conditions
+db.Where("name = ? and age >= ?", "jinzhu", "22").Find(&users)
+//// SELECT * FROM users WHERE name = 'jinzhu' AND age >= 22;
+```
+
+### Where (Struct & Map)
+
+```go
+// Search with struct
 db.Where(&User{Name: "jinzhu", Age: 20}).First(&user)
-//// user -> select * from users name = "jinzhu" and age = 20 limit 1;
-db.Where(map[string]interface{}{"name": "jinzhu", "age": 20}).First(&user)
-//// user -> select * from users name = "jinzhu" and age = 20 limit 1;
-db.Where("birthday < ?", time.Now()).Find(&users)
+//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20 LIMIT 1;
 
-// Not
-db.Not([]int64{1,2,3}).First(&user)
-//// user -> select * from users where id NOT IN (1,2,3)
-db.Not([]int64{}).First(&user)
-//// user -> select * from users;
+// Search with map
+db.Where(map[string]interface{}{"name": "jinzhu", "age": 20}).Find(&users)
+//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20;
+```
+
+### Not
+
+```go
+// Not Equal
 db.Not("name", "jinzhu").First(&user)
-//// user -> select * from users where name <> "jinzhu"
+//// SELECT * FROM users WHERE name <> "jinzhu" LIMIT 1;
+
+// Not In
+db.Not("name", []string{"jinzhu", "jinzhu 2"}).Find(&users)
+//// SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");
+
+// Not In for Primary Key
+db.Not([]int64{1,2,3}).First(&user)
+//// SELECT * FROM users WHERE id NOT IN (1,2,3);
+
+db.Not([]int64{}).First(&user)
+//// SELECT * FROM users;
+
+// Normal SQL
 db.Not("name = ?", "jinzhu").First(&user)
-//// user -> select * from users where NOT(name = "jinzhu")
-db.Not("name <> ?", "jinzhu").First(&user)
-//// user -> select * from users where NOT(name <> "jinzhu")
-db.Not("name", []string{"jinzhu", "jinzhu 2"}).First(&user)
-//// user -> select * from users where name NOT IN ("jinzhu", "jinzhu 2")
+//// SELECT * FROM users WHERE NOT(name = "jinzhu");
+
+// Not With Struct
 db.Not(User{Name: "jinzhu"}).First(&user)
-//// user -> select * from users where name <> "jinzhu";
+//// SELECT * FROM users WHERE name <> "jinzhu";
+```
 
-// Inline search condition
+### Inline Search Condition
+
+```go
+// Find with primary key
 db.First(&user, 23)
-//// user -> select * from users where id = 23 limit 1;
-db.First(&user, "name = ?", "jinzhu")
-//// user -> select * from users where name = "jinzhu" limit 1;
-db.Find(&users, "name = ?", "jinzhu")
-//// users -> select * from users where name = "jinzhu";
+//// SELECT * FROM users WHERE id = 23 LIMIT 1;
+
+// Normal SQL
+db.Find(&user, "name = ?", "jinzhu")
+//// SELECT * FROM users WHERE name = "jinzhu";
+
+// Multiple Conditions
 db.Find(&users, "name <> ? and age > ?", "jinzhu", 20)
-//// users -> select * from users where name <> "jinzhu" and age > 20;
-db.Find(&users, &User{Age: 20})
-//// users -> select * from users where age = 20;
+//// SELECT * FROM users WHERE name <> "jinzhu" AND age > 20;
+
+// Inline Search With Struct
+db.Find(&users, User{Age: 20})
+//// SELECT * FROM users WHERE age = 20;
+
+// Inline Search With Map
 db.Find(&users, map[string]interface{}{"age": 20})
-//// users -> select * from users where age = 20;
+//// SELECT * FROM users WHERE age = 20;
+```
+
+## FirstOrInit
+
+Try to load the first record, if fails, initialize struct with search conditions.
+(only support map or struct conditions, SQL like conditions are not supported)
+
+```go
+db.FirstOrInit(&user, User{Name: "non_existing"})
+//// User{Name: "non_existing"}
 
-// FirstOrInit
-db.FirstOrInit(&user, User{Name: "noexisting_user"})
-//// user -> User{Name: "noexisting_user"}
 db.Where(User{Name: "Jinzhu"}).FirstOrInit(&user)
-//// user -> User{Id: 111, Name: "Jinzhu"}
-db.FirstOrInit(&user, map[string]interface{}{"name": "jinzhu", "age": 20})
-//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
+//// User{Id: 111, Name: "Jinzhu", Age: 20}
 
-// FirstOrInit With Attrs
-db.Where(User{Name: "noexisting_user"}).Attrs(User{Age: 20}).FirstOrInit(&user)
-//// user -> select * from users where name = 'noexisting_user';
-//// If no record found, will assign the attrs to user, so user become:
-////   User{Name: "noexisting_user", Age: 20}
+db.FirstOrInit(&user, map[string]interface{}{"name": "jinzhu"})
+//// User{Id: 111, Name: "Jinzhu", Age: 20}
+```
+
+### FirstOrInit With Attrs
+
+Attr's arguments would be used to initialize struct if not record found, but won't be used for search
+
+```go
+db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrInit(&user)
+//// SELECT * FROM USERS WHERE name = 'non_existing';
+//// User{Name: "non_existing", Age: 20}
+
+// Above code could be simplified if have only one attribute
 db.Where(User{Name: "noexisting_user"}).Attrs("age", 20).FirstOrInit(&user)
-// Same as above
-db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 20}).FirstOrInit(&user)
-//// user -> select * from users where name = 'jinzhu';
-//// If found the user, will ingore the attrs:
-////   User{Id: 111, Name: "Jinzhu", Age: 18}
 
-// FirstOrInit With Assign
-db.Where(User{Name: "noexisting_user"}).Assign(User{Age: 20}).FirstOrInit(&user)
-//// user -> select * from users where name = 'noexisting_user';
-//// If no record found, will assign the value to user, so user become:
-////   User{Name: "noexisting_user", Age: 20} (same as FirstOrInit With Attrs)
-db.Where(User{Name: "noexisting_user"}).Assign("age", 20).FirstOrInit(&user)
-// Same as above
-//// user -> User{Name: "noexisting_user", Age: 20}
-db.Where(User{Name: "Jinzhu"}).Assign(User{Age: 20}).FirstOrInit(&user)
-//// user -> select * from users where name = 'jinzhu';
-//// If found the user, will assign the value to user, so user become: (different with FirstOrInit With Attrs)
+// If record found, Attrs would be ignored
+db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 30}).FirstOrInit(&user)
+//// SELECT * FROM USERS WHERE name = jinzhu';
 ////   User{Id: 111, Name: "Jinzhu", Age: 20}
 
-// FirstOrCreate
-db.FirstOrCreate(&user, User{Name: "noexisting_user"})
-//// user -> User{Id: 112, Name: "noexisting_user"}
+### FirstOrInit With Assign
+
+Assign's arguments would be used to set the struct even record found, but won't be used for search
+
+```go
+db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrInit(&user)
+//// User{Name: "non_existing", Age: 20}
+
+db.Where(User{Name: "Jinzhu"}).Assign(User{Age: 30}).FirstOrInit(&user)
+//// User{Id: 111, Name: "Jinzhu", Age: 30}
+```
+
+## FirstOrCreate
+
+Try to load the first record, if fails, initialize struct with search conditions and save it
+
+```go
+db.FirstOrCreate(&user, User{Name: "non_existing"})
+//// User{Id: 112, Name: "non_existing"}
+
 db.Where(User{Name: "Jinzhu"}).FirstOrCreate(&user)
-//// user -> User{Id: 111, Name: "Jinzhu"}
-db.FirstOrCreate(&user, map[string]interface{}{"name": "jinzhu", "age": 20})
-//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
+//// User{Id: 111, Name: "Jinzhu"}
 
+db.FirstOrCreate(&user, map[string]interface{}{"name": "jinzhu", "age": 30})
+//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
+```
+
+### FirstOrCreate With Attrs
+
+Attr's arguments would be used to initialize struct if not record found, but won't be used for search
+
+```go
 // FirstOrCreate With Attrs
-db.Where(User{Name: "noexisting_user"}).Attrs(User{Age: 20}).FirstOrCreate(&user)
-//// user -> select * from users where name = 'noexisting_user';
-//// If not record found, will assing the attrs to the user first, then create it
-//// Same as db.Where(User{Name: "noexisting_user"}).FirstOrCreate(&user).Update("age": 20), but one less sql
-db.Where(User{Name: "noexisting_user"}).Attrs("age", 20).FirstOrCreate(&user)
-// Save as above
-//// user -> User{Id: 112, Name: "noexisting_user", Age: 20}
-db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 20}).FirstOrCreate(&user)
-//// user -> select * from users where name = 'jinzhu';
-//// If found any record, will ignore the attrs
-//// user -> User{Id: 111, Name: "Jinzhu", Age: 18}
+db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrCreate(&user)
+//// SELECT * FROM users WHERE name = 'non_existing';
+//// User{Id: 112, Name: "non_existing", Age: 20}
 
-// FirstOrCreate With Assign
-db.Where(User{Name: "noexisting_user"}).Assign(User{Age: 20}).FirstOrCreate(&user)
-//// user -> select * from users where name = 'noexisting_user';
-//// If not record found, will assing the value to the user first, then create it
-//// user -> User{Id: 112, Name: "noexisting_user", Age: 20} (Same as FirstOrCreate With Attrs)
-db.Where(User{Name: "Jinzhu"}).Assign(User{Age: 20}).FirstOrCreate(&user)
-//// user -> select * from users where name = 'jinzhu';
-//// If any record found, will assing the value to the user and update it
-//// UPDATE users SET age=20 WHERE id = 111;
-//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
+db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 30}).FirstOrCreate(&user)
+//// User{Id: 111, Name: "Jinzhu", Age: 20}
+```
 
+### FirstOrCreate With Assign
 
+Assign's arguments would be used to initialize the struct if not record found,
+If any record found, will assign those values to the record, and save it back to database.
+
+```go
+db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrCreate(&user)
+//// user -> User{Id: 112, Name: "non_existing", Age: 20}
+
+db.Where(User{Name: "Jinzhu"}).Assign(User{Age: 30}).FirstOrCreate(&user)
+//// UPDATE users SET age=30 WHERE id = 111;
+//// User{Id: 111, Name: "Jinzhu", Age: 30}
+```
+
+### SELECT
+
+```go
 //// user -> User{Id: 111, Name: "Jinzhu", Age: 18}
 //// You must noticed that the Attrs is similar to FirstOrInit with Attrs, yes?
 
@@ -227,10 +366,10 @@ Below callbacks are defined now:
 Callbacks is a function defined to a model, if the function return error, will prevent the database operations.
 
 func (u *User) BeforeUpdate() (err error) {
-  if u.readonly() {
-    err = errors.New("Read Only User")
-  }
-  return
+if u.readonly() {
+err = errors.New("Read Only User")
+}
+return
 }
 
 // Pluck (get users's age as map)
@@ -282,11 +421,11 @@ db.First(&user, 20).Updates(User{Name: "hello", Age: 18})
 // Soft Delete
 // For those struct have DeletedAt field, they will get soft delete ability automatically!
 type Order struct {
-  Id        int64
-  Amount    int64
-  CreatedAt time.Time
-  UpdatedAt time.Time
-  DeletedAt time.Time
+Id        int64
+Amount    int64
+CreatedAt time.Time
+UpdatedAt time.Time
+DeletedAt time.Time
 }
 order := order{Id:10}
 db.Delete(&order)
@@ -350,7 +489,6 @@ db.Where("email = ?", "x@example.org"').Attrs(User{FromIp: "111.111.111.111"}).F
 ```
 
 ## TODO
-* SubStruct
 * Index, Unique, Valiations
 * Auto Migration
 * SQL Log
diff --git a/gorm_test.go b/gorm_test.go
index de9d8dc5..7e76c722 100644
--- a/gorm_test.go
+++ b/gorm_test.go
@@ -12,12 +12,32 @@ import (
 )
 
 type User struct {
-	Id        int64
-	Age       int64
-	Birthday  time.Time
-	Name      string
-	CreatedAt time.Time
-	UpdatedAt time.Time
+	Id                int64     // Id: Primary key
+	Birthday          time.Time // Time
+	Age               int64
+	Name              string
+	CreatedAt         time.Time // CreatedAt: Time of record is created, will be insert automatically
+	UpdatedAt         time.Time // UpdatedAt: Time of record is updated, will be updated automatically
+	DeletedAt         time.Time // DeletedAt: Time of record is deleted, refer Soft Delete for more
+	Email             []Email   // Embedded structs
+	BillingAddress    Address   // Embedded struct
+	BillingAddressId  int64     // Embedded struct's foreign key
+	ShippingAddress   Address   // Embedded struct
+	ShippingAddressId int64     // Embedded struct's foreign key
+}
+
+type Email struct {
+	Id         int64
+	UserId     int64 // Foreign key for above embedded structs
+	Email      string
+	Subscribed bool
+}
+
+type Address struct {
+	Id       int64
+	Address1 string
+	Address2 string
+	Post     string
 }
 
 type Product struct {
@@ -1002,12 +1022,14 @@ type Category struct {
 }
 
 type Post struct {
-	Id         int64
-	CategoryId int64
-	Title      string
-	Body       string
-	Comments   []Comment
-	Category   Category
+	Id             int64
+	CategoryId     int64
+	MainCategoryId int64
+	Title          string
+	Body           string
+	Comments       []Comment
+	Category       Category
+	MainCategory   Category
 }
 
 type Comment struct {
@@ -1027,10 +1049,11 @@ func TestSubStruct(t *testing.T) {
 	db.CreateTable(Comment{})
 
 	post := Post{
-		Title:    "post 1",
-		Body:     "body 1",
-		Comments: []Comment{{Content: "Comment 1"}, {Content: "Comment 2"}},
-		Category: Category{Name: "Category 1"},
+		Title:        "post 1",
+		Body:         "body 1",
+		Comments:     []Comment{{Content: "Comment 1"}, {Content: "Comment 2"}},
+		Category:     Category{Name: "Category 1"},
+		MainCategory: Category{Name: "Main Category 1"},
 	}
 
 	if err := db.Save(&post).Error; err != nil {
@@ -1043,7 +1066,7 @@ func TestSubStruct(t *testing.T) {
 
 	var p Post
 	db.First(&p, post.Id)
-	if post.CategoryId == 0 || p.CategoryId == 0 {
+	if post.CategoryId == 0 || p.CategoryId == 0 || post.MainCategoryId == 0 || p.MainCategoryId == 0 {
 		t.Errorf("Category Id should exist")
 	}
 
@@ -1066,3 +1089,16 @@ func TestSubStruct(t *testing.T) {
 	comment3 := Comment{Content: "Comment 3", Post: Post{Title: "Title 3", Body: "Body 3"}}
 	db.Save(&comment3)
 }
+
+func TestT(t *testing.T) {
+	user := User{Name: "jinzhu", Age: 18, Birthday: time.Now()}
+	db.Save(&user)
+
+	var user2 User
+	db.Where("name in (?)", []string{"1,2"}).First(&user2).Update("name", "hhh")
+	debug(user2)
+
+	var users []User
+	db.Find(&users, User{Age: 20})
+	debug(users)
+}