Define some error codes

README.md

@@ -687,6 +687,9 @@ query := db.First(&user).Limit(10).Find(&users)
 if err := db.Where("name = ?", "jinzhu").First(&user).Error; err != nil {
   // ...
 }
+
+// If no record found, gorm will return RecordNotFound error, you could check it with
+db.Where("name = ?", "hello world").First(&User{}).Error == gorm.RecordNotFound
 ```
 
 ## Advanced Usage With Query Chain

chain.go

@@ -2,7 +2,7 @@ package gorm
 
 import (
 	"errors"
-	"fmt"
+
 	"regexp"
 )
 
@@ -300,7 +300,7 @@ func (s *Chain) RemoveIndex(column string) *Chain {
 func (s *Chain) validSql(str string) (result bool) {
 	result = regexp.MustCompile("^\\s*[\\w\\s,.*()]*\\s*$").MatchString(str)
 	if !result {
-		s.err(errors.New(fmt.Sprintf("SQL is not valid, %s", str)))
+		s.err(InvalidSql)
 	}
 	return
 }

do.go

@@ -395,7 +395,7 @@ func (s *Do) query() {
 		}
 
 		if !has_record && !is_slice {
-			s.err(errors.New("Record not found!"))
+			s.err(RecordNotFound)
 		}
 	}
 }

errors.go

@@ -0,0 +1,8 @@
+package gorm
+
+import "errors"
+
+var (
+	RecordNotFound = errors.New("Record Not Found")
+	InvalidSql     = errors.New("Invalid SQL")
+)

gorm_test.go

@@ -191,18 +191,15 @@ func TestSaveAndUpdate(t *testing.T) {
 
 	user.Name = new_name
 	db.Save(&user)
-	orm := db.Where("name = ?", name).First(&User{})
+	if db.Where("name = ?", name).First(&User{}).Error != RecordNotFound {
-	if orm.Error == nil {
 		t.Errorf("Should raise error when looking for a existing user with an outdated name")
 	}
 
-	orm = db.Where("name = ?", new_name).First(&User{})
+	if db.Where("name = ?", new_name).First(&User{}).Error != nil {
-	if orm.Error != nil {
 		t.Errorf("Shouldn't raise error when looking for a existing user with the new name")
 	}
 
-	orm = db.Where("name = ?", name2).First(&User{})
+	if db.Where("name = ?", name2).First(&User{}).Error != nil {
-	if orm.Error != nil {
 		t.Errorf("Shouldn't update other users")
 	}
 }