164 lines
3.6 KiB
Markdown
164 lines
3.6 KiB
Markdown
# Database
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<!-- toc -->
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## Connecting to a database
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When connect to a database, you need to import the database's driver first, for example:
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```go
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import _ "github.com/go-sql-driver/mysql"
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```
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GORM has wrapped some drivers, for easier to remember the import path, so you could import the mysql driver with
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```go
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import _ "github.com/jinzhu/gorm/dialects/mysql"
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// import _ "github.com/jinzhu/gorm/dialects/postgres"
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// import _ "github.com/jinzhu/gorm/dialects/sqlite"
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// import _ "github.com/jinzhu/gorm/dialects/mssql"
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```
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#### MySQL
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**NOTE** in order to handle `time.Time` you need to include `parseTime` as param [more supported parameters](https://github.com/go-sql-driver/mysql#parameters)
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```go
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import (
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"github.com/jinzhu/gorm"
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_ "github.com/jinzhu/gorm/dialects/mysql"
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)
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func main() {
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db, err := gorm.Open("mysql", "user:password@/dbname?charset=utf8&parseTime=True&loc=Local")
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}
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```
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#### PostgreSQL
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```go
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import (
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"github.com/jinzhu/gorm"
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_ "github.com/jinzhu/gorm/dialects/postgres"
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)
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func main() {
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db, err := gorm.Open("postgres", "user=gorm dbname=gorm sslmode=disable")
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}
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```
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#### Sqlite3
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```go
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import (
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"github.com/jinzhu/gorm"
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_ "github.com/jinzhu/gorm/dialects/sqlite"
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)
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func main() {
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db, err := gorm.Open("sqlite3", "/tmp/gorm.db")
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}
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```
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#### Write Dialect for unsupported databases
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GORM officially support above databases, but you could write a dialect for those unsupported databaes,
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Refer: [https://github.com/jinzhu/gorm/blob/master/dialect.go](https://github.com/jinzhu/gorm/blob/master/dialect.go)
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## Migration
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### Auto Migration
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Automatically migrate your schema, to keep your schema update to date
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**WARNING** AutoMigrate will ONLY create tables, missing columns and missing indexes, **WON'T** change existing column's type or delete unused columns to protect your data
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```go
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db.AutoMigrate(&User{})
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db.AutoMigrate(&User{}, &Product{}, &Order{})
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// Add table suffix when create tables
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db.Set("gorm:table_options", "ENGINE=InnoDB").AutoMigrate(&User{})
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```
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### Has Table
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```go
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// Check model `User`'s table exists or not
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db.HasTable(&User{})
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// Check table `users` exists or not
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db.HasTable("users")
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```
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### Create Table
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```go
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// Create table for model `User`
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db.CreateTable(&User{})
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// will append "ENGINE=InnoDB" to the SQL statement when creating table `users`
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db.Set("gorm:table_options", "ENGINE=InnoDB").CreateTable(&User{})
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```
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### Drop table
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```go
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// Drop model `User`'s table
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db.DropTable(&User{})
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// Drop table `users
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db.DropTable("users")
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// Drop model's `User`'s table and table `products`
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db.DropTableIfExists(&User{}, "products")
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```
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### ModifyColumn
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Modify column's type to given value
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```go
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// change column description's data type to `text` for model `User`
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db.Model(&User{}).ModifyColumn("description", "text")
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```
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### DropColumn
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```go
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// Drop column description from model `User`
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db.Model(&User{}).DropColumn("description")
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```
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### Add Foreign Key
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```go
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// Add foreign key
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// 1st param : foreignkey field
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// 2nd param : destination table(id)
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// 3rd param : ONDELETE
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// 4th param : ONUPDATE
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db.Model(&User{}).AddForeignKey("city_id", "cities(id)", "RESTRICT", "RESTRICT")
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```
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### Indexes
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```go
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// Add index for columns `name` with given name `idx_user_name`
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db.Model(&User{}).AddIndex("idx_user_name", "name")
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// Add index for columns `name`, `age` with given name `idx_user_name_age`
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db.Model(&User{}).AddIndex("idx_user_name_age", "name", "age")
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// Add unique index
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db.Model(&User{}).AddUniqueIndex("idx_user_name", "name")
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// Add unique index for multiple columns
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db.Model(&User{}).AddUniqueIndex("idx_user_name_age", "name", "age")
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// Remove index
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db.Model(&User{}).RemoveIndex("idx_user_name")
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```
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