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GORM/GEN

The code generator base on GORM, aims to be developer friendly.

Overview

  • CRUD or DIY query method code generation
  • Auto migration from database to code
  • Transactions, Nested Transactions, Save Point, RollbackTo to Saved Point
  • Competely compatible with GORM
  • Developer Friendly

Installation

To install Gen package, you need to install Go and set your Go workspace first.

  1. The first need Go installed(version 1.14+ is required), then you can use the below Go command to install Gen.
go get -u gorm.io/gen
  1. Import it in your code:
import "gorm.io/gen"

Quick start

# assume the following code in generate.go file
$ cat generate.go
package main

import "gorm.io/gen"

// generate code
func main() {
    // specify the output directory (default: "./query")
    g := gen.NewGenerator(gen.Config{OutPath: "../dal/query"})
  
    // reuse the database connection in Project or create a connection here
    // db, _ := gorm.Open(mysql.Open("root:@(127.0.0.1:3306)/demo?charset=utf8mb4&parseTime=True&loc=Local"))
    g.UseDB(db)
  
    // apply basic crud api on structs or table models which is specified by table name with function
    // GenerateModel/GenerateModelAs. And generator will generate table models' code when calling Excute.
    g.ApplyBasic(model.User{}, g.GenerateModel("company"), g.GenerateModelAs("people", "Person"),)
    
    // apply diy interfaces on structs or table models
    g.ApplyInterface(func(method model.Method) {}, model.User{}, g.GenerateModel("company"))

    // execute the action of code generation
    g.Execute()
}

Project Directory

Here is a template for best practices:

demo
├── cmd
│   └── generate
│       └── generate.go # execute it will generate codes
├── dal
│   ├── dal.go # create connections with database server here
│   └── model
│   │   ├── method.go # DIY method interfaces
│   │   └── model.go  # store struct which corresponding to the database table
│   └── query  # generated code's directory
│       └── gorm_generated.go # generated code
├── biz
│   └── query.go # call function in dal/gorm_generated.go and query databases
├── config
│   └── config.go # DSN for database server
├── generate.sh # a shell to execute cmd/generate
├── go.mod
├── go.sum
└── main.go

API Examples

Field Expression

Create Field

Actually, you're not supposed to create a new field variable, cause it will be accomplished in generated code.

Field Type Detail Type Crerate Function Supported Query Method
generic field NewField IsNull/IsNotNull/Count
int int/int8/.../int64 NewInt/NewInt8/.../NewInt64 Eq/Neq/Gt/Gte/Lt/Lte/In/NotIn/Between/NotBetween/Like/NotLike/Add/Sub/Mul/Div/Mod/FloorDiv/RightShift/LeftShift/BitXor/BitAnd/BitOr/BitFlip
uint uint/uint8/.../uint64 NewUint/NewUint8/.../NewUint64 same with int
float float32/float64 NewFloat32/NewFloat64 Eq/Neq/Gt/Gte/Lt/Lte/In/NotIn/Between/NotBetween/Like/NotLike/Add/Sub/Mul/Div/FloorDiv
string string/[]byte NewString/NewBytes Eq/Neq/Gt/Gte/Lt/Lte/Between/NotBetween/In(val/NotIn(val/Like/NotLike/Regexp/NotRegxp
bool bool NewBool Not/Is/And/Or/Xor/BitXor/BitAnd/BitOr
time time.Time NewTime Eq/Neq/Gt/Gte/Lt/Lte/Between/NotBetween/In/NotIn/Add/Sub

Create field examples:

import "gorm.io/gen/field"

// create a new generic field map to `generic_a`
a := field.NewField("table_name", "generic_a")

// create a field map to `id`
i := field.NewInt("user", "id")

// create a field map to `address`
s := field.NewString("user", "address")

// create a field map to `create_time`
t := field.NewTime("user", "create_time")

CRUD API

Here is a basic struct user and struct DB.

// generated code
// generated code
// generated code
package query

import "gorm.io/gen"

// struct map to table `users` 
type user struct {
    gen.DO
    ID       field.Uint
    Name     field.String
    Age      field.Int
    Address  field.Field
    Birthday field.Time
}

// struct collection
type DB struct {
    db       *gorm.DB
    User     *user
}

Create

Create Record
// u refer to query.user
user := model.User{Name: "Modi", Age: 18, Birthday: time.Now()}

u := query.Query.User
err := u.Create(&user) // pass pointer of data to Create

err // returns error
Create Record With Selected Fields

Create a record and assgin a value to the fields specified.

u := query.Query.User
u.Select(u.Name, u.Age).Create(&user)
// INSERT INTO `users` (`name`,`age`) VALUES ("modi", 18)

Create a record and ignore the values for fields passed to omit

u := query.Query.User
u.Omit(u.Name, u.Age).Create(&user)
// INSERT INTO `users` (`Address`, `Birthday`) VALUES ("2021-08-17 20:54:12.000", 18)
Batch Insert

To efficiently insert large number of records, pass a slice to the Create method. GORM will generate a single SQL statement to insert all the data and backfill primary key values.

var users = []model.User{{Name: "modi"}, {Name: "zhangqiang"}, {Name: "songyuan"}}
query.Query.User.Create(&users)

for _, user := range users {
    user.ID // 1,2,3
}

You can specify batch size when creating with CreateInBatches, e.g:

var users = []User{{Name: "modi_1"}, ...., {Name: "modi_10000"}}

// batch size 100
query.Query.User.CreateInBatches(users, 100)

It will works if you set CreateBatchSize in gorm.Config / gorm.Session

db, err := gorm.Open(sqlite.Open("gorm.db"), &gorm.Config{
    CreateBatchSize: 1000,
})
// OR
db = db.Session(&gorm.Session{CreateBatchSize: 1000})

u := query.NewUser(db)

var users = []User{{Name: "modi_1"}, ...., {Name: "modi_5000"}}

u.Create(&users)
// INSERT INTO users xxx (5 batches)

Query

Retriving a single object

Generated code provides First, Take, Last methods to retrieve a single object from the database, it adds LIMIT 1 condition when querying the database, and it will return the error ErrRecordNotFound if no record is found.

u := query.Query.User

// Get the first record ordered by primary key
user, err := u.First()
// SELECT * FROM users ORDER BY id LIMIT 1;

// Get one record, no specified order
user, err := u.Take()
// SELECT * FROM users LIMIT 1;

// Get last record, ordered by primary key desc
user, err := db.Last()
// SELECT * FROM users ORDER BY id DESC LIMIT 1;

// check error ErrRecordNotFound
errors.Is(err, gorm.ErrRecordNotFound)
Retrieving objects with primary key
u := query.Query.User

user, err := u.First(u.ID.Eq(10))
// SELECT * FROM users WHERE id = 10;

users, err := u.Find(u.ID.In(1,2,3))
// SELECT * FROM users WHERE id IN (1,2,3);

If the primary key is a string (for example, like a uuid), the query will be written as follows:

user, err := db.First(u.ID.Eq("1b74413f-f3b8-409f-ac47-e8c062e3472a"))
// SELECT * FROM users WHERE id = "1b74413f-f3b8-409f-ac47-e8c062e3472a";
Retrieving all objects
u := query.Query.User

// Get all records
users, err := u.Find()
// SELECT * FROM users;
Conditions
String Conditions
u := query.Query.User

// Get first matched record
user, err := u.Where(u.Name.Eq("modi")).First()
// SELECT * FROM users WHERE name = 'modi' ORDER BY id LIMIT 1;

// Get all matched records
users, err := u.Where(u.Name.Neq("modi")).Find()
// SELECT * FROM users WHERE name <> 'modi';

// IN
users, err := u.Where(u.Name.In("modi", "zhangqiang")).Find()
// SELECT * FROM users WHERE name IN ('modi','zhangqiang');

// LIKE
users, err := u.Where(u.Name.Like("%modi%")).Find()
// SELECT * FROM users WHERE name LIKE '%modi%';

// AND
users, err := u.Where(u.Name.Eq("modi"), u.Age.Gte(17)).Find()
// SELECT * FROM users WHERE name = 'modi' AND age >= 17;

// Time
users, err := u.Where(u.Birthday.Gt(birthTime).Find()
// SELECT * FROM users WHERE birthday > '2000-01-01 00:00:00';

// BETWEEN
users, err := u.Where(u.Birthday.Between(lastWeek, today)).Find()
// SELECT * FROM users WHERE birthday BETWEEN '2000-01-01 00:00:00' AND '2000-01-08 00:00:00';
Inline Condition
u := query.Query.User

// Get by primary key if it were a non-integer type
user, err := u.First(u.ID.Eq("string_primary_key"))
// SELECT * FROM users WHERE id = 'string_primary_key';

// Plain SQL
users, err := u.Find(u.Name.Eq("modi"))
// SELECT * FROM users WHERE name = "modi";

users, err := u.Find(u.Name.Neq("modi"), u.Age.Gt(17))
// SELECT * FROM users WHERE name <> "modi" AND age > 17;
Not Conditions

Build NOT conditions, works similar to Where

u := query.Query.User

user, err := u.Not(u.Name.Eq("modi")).First()
// SELECT * FROM users WHERE NOT name = "modi" ORDER BY id LIMIT 1;

// Not In
users, err := u.Not(u.Name.In("modi", "zhangqiang")).Find()
// SELECT * FROM users WHERE name NOT IN ("modi", "zhangqiang");

// Not In slice of primary keys
user, err := u.Not(u.ID.In(1,2,3)).First()
// SELECT * FROM users WHERE id NOT IN (1,2,3) ORDER BY id LIMIT 1;
Or Conditions
u := query.Query.User

users, err := u.Where(u.Role.Eq("admin")).Or(u.Role.Eq("super_admin")).Find()
// SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';
Group Conditions

Easier to write complicated SQL query with Group Conditions

p := query.Query.Pizza

pizzas, err := p.Where(
    p.Where(p.Pizza.Eq("pepperoni")).Where(p.Where(p.Size.Eq("small")).Or(p.Size.Eq("medium"))),
).Or(
    p.Where(p.Pizza.Eq("hawaiian")).Where(p.Size.Eq("xlarge")),
).Find()

// SELECT * FROM `pizzas` WHERE (pizza = "pepperoni" AND (size = "small" OR size = "medium")) OR (pizza = "hawaiian" AND size = "xlarge")
Selecting Specific Fields

Select allows you to specify the fields that you want to retrieve from database. Otherwise, GORM will select all fields by default.

u := query.Query.User

users, err := u.Select(u.Name, u.Age).Find()
// SELECT name, age FROM users;

u.Select(u.Age.Avg()).Rows()
// SELECT Avg(age) FROM users;
Order

Specify order when retrieving records from the database

u := query.Query.User

users, err := u.Order(u.Age.Desc(), u.Name).Find()
// SELECT * FROM users ORDER BY age DESC, name;

// Multiple orders
users, err := u.Order(u.Age.Desc()).Order(u.Name).Find()
// SELECT * FROM users ORDER BY age DESC, name;
Limit & Offset

Limit specify the max number of records to retrieve Offset specify the number of records to skip before starting to return the records

u := query.Query.User

urers, err := u.Limit(3).Find()
// SELECT * FROM users LIMIT 3;

// Cancel limit condition with -1
users, err := u.Limit(10).Limit(-1).Find()
// SELECT * FROM users;

users, err := u.Offset(3).Find()
// SELECT * FROM users OFFSET 3;

users, err := u.Limit(10).Offset(5).Find()
// SELECT * FROM users OFFSET 5 LIMIT 10;

// Cancel offset condition with -1
users, err := u.Offset(10).Offset(-1).Find()
// SELECT * FROM users;
Group By & Having
u := query.Query.User

type Result struct {
    Date  time.Time
    Total int
}

var result Result

err := u.Select(u.Name, u.Age.Sum().As("total")).Where(u.Name.Like("%modi%")).Group(u.Name).Scan(&result)
// SELECT name, sum(age) as total FROM `users` WHERE name LIKE "group%" GROUP BY `name`

err := u.Select(u.Name, u.Age.Sum().As("total")).Group(u.Name).Having(u.Name.Eq("group")).Scan(&result)
// SELECT name, sum(age) as total FROM `users` GROUP BY `name` HAVING name = "group"

rows, err := u.Select(u.Birthday.As("date"), u.Age.Sum().As("total")).Group(u.Birthday).Rows()
for rows.Next() {
  ...
}

o := query.Query.Order

rows, err := o.Select(o.CreateAt.Date().As("date"), o.Amount.Sum().As("total")).Group(o.CreateAt.Date()).Having(u.Amount.Sum().Gt(100)).Rows()
for rows.Next() {
  ...
}

var results []Result

o.Select(o.CreateAt.Date().As("date"), o.Amount.Sum().As("total")).Group(o.CreateAt.Date()).Having(u.Amount.Sum().Gt(100)).Scan(&results)
Distinct

Selecting distinct values from the model

u := query.Query.User

users, err := u.Distinct(u.Name, u.Age).Order(u.Name, u.Age.Desc()).Find()

Distinct works with Pluck and Count too

Joins

Specify Joins conditions

u := query.Query.User
e := query.Query.Email
c := query.Query.CreditCard

type Result struct {
    Name  string
    Email string
}

var result Result

err := u.Select(u.Name, e.Email).LeftJoin(e, e.UserId.EqCol(u.ID)).Scan(&result)
// SELECT users.name, emails.email FROM `users` left join emails on emails.user_id = users.id

rows, err := u.Select(u.Name, e.Email).LeftJoin(e, e.UserId.EqCol(u.ID)).Rows()
for rows.Next() {
  ...
}

var results []Result

err := u.Select(u.Name, e.Email).LeftJoin(e, e.UserId.EqCol(u.ID)).Scan(&results)

// multiple joins with parameter
users := u.Join(e, e.UserId.EqCol(u.id), e.Email.Eq("[email protected]")).Join(c, c.UserId.EqCol(u.ID)).Where(c.Number.Eq("411111111111")).Find()
SubQuery

A subquery can be nested within a query, GEN can generate subquery when using a Dao object as param

o := query.Query.Order
u := query.Query.User

orders, err := o.Where(gen.Gt(o.Amount, o.Select(u.Amount.Avg())).Find()
// SELECT * FROM "orders" WHERE amount > (SELECT AVG(amount) FROM "orders");

subQuery := u.Select(u.Age.Avg()).Where(u.Name.Like("name%"))
users, err := u.Select(u.Age.Avg().As("avgage")).Group(u.Name).Having(gen.Gt(u.Age.Avg(), subQuery).Find()
// SELECT AVG(age) as avgage FROM `users` GROUP BY `name` HAVING AVG(age) > (SELECT AVG(age) FROM `users` WHERE name LIKE "name%")
From SubQuery

GORM allows you using subquery in FROM clause with method Table, for example:

u := query.Query.User
p := query.Query.Pet

users, err := gen.Table(u.Select(u.Name, u.Age).As("u")).Where(u.Age.Eq(18)).Find()
// SELECT * FROM (SELECT `name`,`age` FROM `users`) as u WHERE `age` = 18

subQuery1 := u.Select(u.Name)
subQuery2 := p.Select(p.Name)
users, err := gen.Table(subQuery1.As("u"), subQuery2.As("p")).Find()
db.Table("(?) as u, (?) as p", subQuery1, subQuery2).Find(&User{})
// SELECT * FROM (SELECT `name` FROM `users`) as u, (SELECT `name` FROM `pets`) as p
Update from SubQuery

Update a table by using SubQuery

u := query.Query.User
c := query.Query.Company

u.Update(u.CompanyName, c.Select(c.Name).Where(c.ID.EqCol(u.CompanyId)))
// UPDATE "users" SET "company_name" = (SELECT name FROM companies WHERE companies.id = users.company_id);

u.Where(u.Name.Eq("modi")).Update(u.CompanyName, c.Select(c.Name).Where(c.ID.EqCol(u.CompanyId)))
Advanced Query
Iteration

GEN supports iterating through Rows

rows, err := query.Query.User.Where("name = ?", "modi").Rows()
defer rows.Close()

for rows.Next() {
    var user User
    // ScanRows is a method of `gorm.DB`, it can be used to scan a row into a struct
    db.ScanRows(rows, &user)

    // do something
}
FindInBatches

Query and process records in batch

u := query.Query.User

// batch size 100
err := u.Where(u.ID.Gt(9)).FindInBatches(&results, 100, func(tx gen.Dao, batch int) error {
    for _, result := range results {
      // batch processing found records
    }
  
    // build a new `u` to use it's api
    // queryUsery := query.NewUser(tx.UnderlyingDB())

    tx.Save(&results)

    batch // Batch 1, 2, 3

    // returns error will stop future batches
    return nil
})
Pluck

Query single column from database and scan into a slice, if you want to query multiple columns, use Select with Scan instead

u := query.Query.User

var ages []int64
u.Pluck(u.Age, &ages)

var names []string
u.Pluck(u.Name, &names)

// Distinct Pluck
u.Distinct().Pluck(u.Name, &names)
// SELECT DISTINCT `name` FROM `users`

// Requesting more than one column, use `Scan` or `Find` like this:
db.Select(u.Name, u.Age).Scan(&users)
users, err := db.Select(u.Name, u.Age).Find()
Scopes

Scopes allows you to specify commonly-used queries which can be referenced as method calls

o := query.Query.Order

func AmountGreaterThan1000(tx gen.Dao) gen.Dao {
    return tx.Where(o.Amount.Gt(1000))
}

func PaidWithCreditCard(tx gen.Dao) gen.Dao {
    return tx.Where(o.PayModeSign.Eq("C"))
}

func PaidWithCod(tx gen.Dao) gen.Dao {
    return tx.Where(o.PayModeSign.Eq("C"))
}

func OrderStatus(status []string) func (tx gen.Dao) gen.Dao {
    return func (tx gen.Dao) gen.Dao {
      return tx.Where(o.Status.In(status...))
    }
}

orders, err := o.Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find()
// Find all credit card orders and amount greater than 1000

orders, err := o.Scopes(AmountGreaterThan1000, PaidWithCod).Find()
// Find all COD orders and amount greater than 1000

orders, err := o.Scopes(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Find()
// Find all paid, shipped orders that amount greater than 1000
Count

Get matched records count

u := query.Query.User

count, err := u.Where(u.Name.Eq("modi")).Or(u.Name.Eq("zhangqiang")).Count()
// SELECT count(1) FROM users WHERE name = 'modi' OR name = 'zhangqiang'

count, err := u.Where(u.Name.Eq("modi")).Count()
// SELECT count(1) FROM users WHERE name = 'modi'; (count)

// Count with Distinct
u.Distinct(u.Name).Count()
// SELECT COUNT(DISTINCT(`name`)) FROM `users`

Update

Update single column

When updating a single column with Update, it needs to have any conditions or it will raise error ErrMissingWhereClause, for example:

u := query.Query.User

// Update with conditions
u.Where(u.Activate.Is(true)).Update(u.Name, "hello")
// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE active=true;

// Update with conditions
u.Where(u.Activate.Is(true)).Update(u.Age, u.Age.Add(1))
// UPDATE users SET age=age+1, updated_at='2013-11-17 21:34:10' WHERE active=true;
Updates multiple columns

Updates supports update with struct or map[string]interface{}, when updating with struct it will only update non-zero fields by default

u := query.Query.User

// Update attributes with `struct`, will only update non-zero fields
u.Updates(User{Name: "hello", Age: 18, Active: false})
// UPDATE users SET name='hello', age=18, updated_at = '2013-11-17 21:34:10' WHERE id = 111;

// Update attributes with `map`
u).Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
// UPDATE users SET name='hello', age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

NOTE When update with struct, GEN will only update non-zero fields, you might want to use map to update attributes or use Select to specify fields to update

Update Selected Fields

If you want to update selected fields or ignore some fields when updating, you can use Select, Omit

// Select with Map
// User's ID is `111`:
db.Model(&user).Select("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
// UPDATE users SET name='hello' WHERE id=111;

db.Model(&user).Omit("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
// UPDATE users SET age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

// Select with Struct (select zero value fields)
db.Model(&user).Select("Name", "Age").Updates(User{Name: "new_name", Age: 0})
// UPDATE users SET name='new_name', age=0 WHERE id=111;

// Select all fields (select all fields include zero value fields)
db.Model(&user).Select("*").Update(User{Name: "jinzhu", Role: "admin", Age: 0})

// Select all fields but omit Role (select all fields include zero value fields)
db.Model(&user).Select("*").Omit("Role").Update(User{Name: "jinzhu", Role: "admin", Age: 0})

Delete

Delete a Record
e := query.Query.Email

// Email's ID is `10`
e.Delete(e.ID.Eq(10))
// DELETE from emails where id = 10;

// Delete with additional conditions
e.Where(e.Name.Eq("modi")).Delete(e.ID.Eq(10))
// DELETE from emails where id = 10 AND name = "modi";
Delete with primary key

GEN allows to delete objects using primary key(s) with inline condition, it works with numbers.

u.Delete(u.ID.In(1,2,3))
// DELETE FROM users WHERE id IN (1,2,3);
Batch Delete

The specified value has no primary value, GEN will perform a batch delete, it will delete all matched records

e := query.Query.Email

err := e.Where(e.Name.Like("%modi%")).Delete()
// DELETE from emails where email LIKE "%modi%";

err := e.Delete(e.Name.Like("%modi%"))
// DELETE from emails where email LIKE "%jinzhu%";
Soft Delete

If your model includes a gorm.DeletedAt field (which is included in gorm.Model), it will get soft delete ability automatically!

When calling Delete, the record WON’T be removed from the database, but GORM will set the DeletedAt‘s value to the current time, and the data is not findable with normal Query methods anymore.

// Batch Delete
u.Where(u.Age.Eq(20)).Delete()
// UPDATE users SET deleted_at="2013-10-29 10:23" WHERE age = 20;

// Soft deleted records will be ignored when querying
u.Where(u.Age.Eq(20)).Delete()
// SELECT * FROM users WHERE age = 20 AND deleted_at IS NULL;

If you don’t want to include gorm.Model, you can enable the soft delete feature like:

type User struct {
    ID      int
    Deleted gorm.DeletedAt
    Name    string
}
Find soft deleted records

You can find soft deleted records with Unscoped

users, err := db.Unscoped().Where(u.Age.Eq(20)).Find()
// SELECT * FROM users WHERE age = 20;
Delete permanently

You can delete matched records permanently with Unscoped

o.Unscoped().Delete(o.ID.Eq(10))
// DELETE FROM orders WHERE id=10;

DIY method

Method interface

Method interface is an abstraction of query methods, all functions it contains are query methods and above comments describe the specific query conditions or logic.
SQL supports simple where query or execute complete SQL, simple query the condition is wrapped in where(), execute complete SQL is wrapped in sql(), or you can omit, write the complete SQL directly.

type Method interface {
    // where("name=@name and age=@age")
    SimpleFindByNameAndAge(name string, age int) (gen.T, error)
    
    // sql(select * from users where id=@id)
    FindUserToMap(id int) (gen.M, error)
    
    // insert into users (name,age) values (@name,@age)
    InsertValue(age int, name string) error
}

Return values must contains less than 1 gen.T/gen.M and less than 1 error. You can also use the basic field(like string int) as the return parameter，gen.T represents return a single result, []gen.T represents return an array of multiple results，

Syntax of template
placeholder
  • gen.T represents specified struct or table
  • gen.M represents map[string]interface
  • @@table represents table's name(if method's parameter doesn't contains variable table, GEN will generate table from model struct)
  • @<columnName> represents column's name or table's name
  • @<name> represents variable
template

Logical operations must be wrapped in {{}},and end must used {{end}}, All templates support nesting

  • if else if else the condition supports a bool parameter or operation expression. The expression support go syntax
  • where The where element inserts where clause only if the child element returns anything. It will be removed if clause starts with and or or, where element removes them. If there is no connector between clauses,GEN will be automatically add and
  • Set The set element inserts set clause only if the child element returns anything. It will be removed if clause starts with ,, where element removes them. If there is no connector between clauses,GEN will be automatically add ,
  • ... Coming soon
If clause
{{if cond1}}{{else if cond2}}{{else}}{{end}}
Raw
// select * from users where {{if name !=""}} name=@name{{end}}
methond(name string)(gen.T,error)
Raw template
select * from @@table where
{{if age>60}}
    status="older"
{{else if age>30}}
    status="middle-ager"
{{else if age>18}}
    status="younger"
{{else}}
    {{if sex=="male"}}
        status="boys"
    {{else}}
        status="girls"
    {{end}}
{{end}}
Where clause
{{where}}{{end}}
Raw
// select * from {{where}}id=@id{{end}}
methond(id int) error
Raw template
select * from @@table 
{{where}}
    {{if cond}}id=@id {{end}}
    {{if name != ""}}@@key=@value{{end}}
{{end}}
Set clause
{{set}}{{end}}
Raw
// update users {{set}}name=@name{{end}}
methond() error
Raw template
update @@table 
{{set}}
    {{if name!=""}} name=@name {{end}}
    {{if age>0}} age=@age {{end}}
{{end}}
where id=@id
Method example
type Method interface {
    // Where("name=@name and age=@age")
    SimpleFindByNameAndAge(name string, age int) (gen.T, error)
    
    // select * from users where id=@id
    FindUserToMap(id int) (gen.M, error)
    
    //sql(insert into @@table (name,age) values (@name,@age) )
    InsertValue(age int, name string) error
    
    // select name from @@table where id=@id
    FindNameById(id int) string
    
    //select * from @@table
    //  {{where}}
    //      id>0
    //      {{if cond}}id=@id {{end}}
    //      {{if key!="" && value != ""}} or @@key=@value{{end}}
    //  {{end}}
    FindByIDOrCustom(cond bool, id int, key, value string) ([]gen.T, error)
    
    //update @@table
    //  {{set}}
    //      update_time=now()
    //      {{if name != ""}}
    //          name=@name
    //      {{end}}
    //  {{end}}
    //  {{where}}
    //      id=@id
    //  {{end}}
    UpdateName(name string, id int) error
}

Smart Select Fields

GEN allows select specific fields with Select, if you often use this in your application, maybe you want to define a smaller struct for API usage which can select specific fields automatically, for example:

type User struct {
  ID     uint
  Name   string
  Age    int
  Gender string
  // hundreds of fields
}

type APIUser struct {
  ID   uint
  Name string
}

type Method interface{
    // select * from user
    FindSome() ([]APIUser, error)
}

apiusers, err := u.Limit(10).FindSome()
// SELECT `id`, `name` FROM `users` LIMIT 10

Advanced Topics

Hints

Optimizer hints allow to control the query optimizer to choose a certain query execution plan, GORM supports it with gorm.io/hints, e.g:

import "gorm.io/hints"

u := query.Query.User

users, err := u.Hints(hints.New("MAX_EXECUTION_TIME(10000)")).Find()
// SELECT * /*+ MAX_EXECUTION_TIME(10000) */ FROM `users`

Index hints allow passing index hints to the database in case the query planner gets confused.

import "gorm.io/hints"

u := query.Query.User

users, err := u.Hints(hints.UseIndex("idx_user_name")).Find()
// SELECT * FROM `users` USE INDEX (`idx_user_name`)

users, err := u.Hints(hints.ForceIndex("idx_user_name", "idx_user_id").ForJoin()).Find()
// SELECT * FROM `users` FORCE INDEX FOR JOIN (`idx_user_name`,`idx_user_id`)"

Contributing

You can help to deliver a better GORM/GEN

License

Released under the MIT License

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Gen: Friendly & Safer GORM powered by Code Generation

gorm.io/gen/

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