sqlc/docs/tutorials/getting-started-mysql.md

Getting started with MySQL

This tutorial assumes that the latest version of sqlc is installed and ready to use.

We'll generate Go code here, but other language plugins are available. You'll naturally need the Go toolchain if you want to build and run a program with the code sqlc generates, but sqlc itself has no dependencies.

Setting up

Create a new directory called sqlc-tutorial and open it up.

Initialize a new Go module named tutorial.sqlc.dev/app

go mod init tutorial.sqlc.dev/app

sqlc looks for either a sqlc.(yaml|yml) or sqlc.json file in the current directory. In our new directory, create a file named sqlc.yaml with the following contents:

version: "2"
sql:
  - engine: "mysql"
    queries: "query.sql"
    schema: "schema.sql"
    gen:
      go:
        package: "tutorial"
        out: "tutorial"

Schema and queries

sqlc needs to know your database schema and queries in order to generate code. In the same directory, create a file named schema.sql with the following content:

CREATE TABLE authors (
  id   BIGINT  NOT NULL AUTO_INCREMENT PRIMARY KEY,
  name text    NOT NULL,
  bio  text
);

Next, create a query.sql file with the following four queries:

-- name: GetAuthor :one
SELECT * FROM authors
WHERE id = ? LIMIT 1;

-- name: ListAuthors :many
SELECT * FROM authors
ORDER BY name;

-- name: CreateAuthor :execresult
INSERT INTO authors (
  name, bio
) VALUES (
  ?, ?
);

-- name: DeleteAuthor :exec
DELETE FROM authors
WHERE id = ?;

Generating code

You are now ready to generate code. You shouldn't see any output when you run the generate subcommand, unless something goes wrong:

sqlc generate

You should now have a tutorial subdirectory with three files containing Go source code. These files comprise a Go package named tutorial:

├── go.mod
├── query.sql
├── schema.sql
├── sqlc.yaml
└── tutorial
    ├── db.go
    ├── models.go
    └── query.sql.go

Using generated code

You can use your newly-generated tutorial package from any Go program. Create a file named tutorial.go and add the following contents:

package main

import (
	"context"
	"database/sql"
	"log"
	"reflect"

	_ "github.com/go-sql-driver/mysql"

	"tutorial.sqlc.dev/app/tutorial"
)

func run() error {
	ctx := context.Background()

	db, err := sql.Open("mysql", "user:password@/dbname?parseTime=true")
	if err != nil {
		return err
	}

	queries := tutorial.New(db)

	// list all authors
	authors, err := queries.ListAuthors(ctx)
	if err != nil {
		return err
	}
	log.Println(authors)

	// create an author
	result, err := queries.CreateAuthor(ctx, tutorial.CreateAuthorParams{
		Name: "Brian Kernighan",
		Bio:  sql.NullString{String: "Co-author of The C Programming Language and The Go Programming Language", Valid: true},
	})
	if err != nil {
		return err
	}

	insertedAuthorID, err := result.LastInsertId()
	if err != nil {
		return err
	}
	log.Println(insertedAuthorID)

	// get the author we just inserted
	fetchedAuthor, err := queries.GetAuthor(ctx, insertedAuthorID)
	if err != nil {
		return err
	}

	// prints true
	log.Println(reflect.DeepEqual(insertedAuthorID, fetchedAuthor.ID))
	return nil
}

func main() {
	if err := run(); err != nil {
		log.Fatal(err)
	}
}

Before this code will compile you'll need to fetch the relevant MySQL driver:

go get github.com/go-sql-driver/mysql
go build ./...

The program should compile without errors. To make that possible, sqlc generates readable, idiomatic Go code that you otherwise would've had to write yourself. Take a look in tutorial/query.sql.go.

Of course for this program to run successfully you'll need to compile after replacing the database connection parameters in the call to sql.Open() with the correct parameters for your database. And your database must have the authors table as defined in schema.sql.

You should now have a working program using sqlc's generated Go source code, and hopefully can see how you'd use sqlc in your own real-world applications.