QL

The ql adapter for QL wraps the github.com/cznic/ql/ql driver written by Jan Mercl.

Before starting to read this detailed information, it is advisable that you take a look at the getting started page so you become acquainted with the basics of upper/db, and you can grasp concepts better.

Installation

Use go get to download and install the adapter:

go get github.com/upper/db/adapter/ql

Setup

Import the ql package into your application:

// main.go
package main

import (
  "github.com/upper/db/adapter/ql"
)

Define the ql.ConnectionURL{} struct:

// ConnectionURL defines the DSN attributes.
type ConnectionURL struct {
  Database string
  Options  map[string]string
}

Pass the ql.ConnectionURL value as argument to ql.Open() so the session is created.

settings = ql.ConnectionURL{
  ...
}

sess, err = ql.Open(settings)
...

Use the ql.ParseURL() function to convert a DSN into a ql.ConnectionURL:

// ParseURL parses a DSN into a ConnectionURL struct.
ql.ParseURL(dsn string) (ConnectionURL, error)

Once the connection is established, you can start performing operations on the database.

Example

In the following example, a table named ‘birthday’ consisting of two columns (‘name’ and ‘born’) will be created. Before starting, the table will be searched in the database and, in the event it already exists, it will be removed. Then, three rows will be inserted into the table and checked for accuracy. To this end, the database will be queried and the matches (insertions) will be printed to standard output.

The birthday table with the name and born columns is created with these SQL statements:

--' example.sql
DROP TABLE IF EXISTS birthday;

CREATE TABLE birthday (
  name string,
  born time
);

The ql command line tool is used to create an example.db database file:

rm -f example.db
cat example.sql | ql -db example.db

The rows are inserted into the birthday table. The database is queried for the insertions and is set to print them to standard output.

package main

import (
	"fmt"
	"log"
	"time"

	"github.com/upper/db/adapter/ql"
)

var settings = ql.ConnectionURL{
	Database: `example.db`, // Path to database file
}

type Birthday struct {
	// The 'name' column of the 'birthday' table
	// is mapped to the 'name' property.
	Name string `db:"name"`
	// The 'born' column of the 'birthday' table
	// is mapped to the 'born' property.
	Born time.Time `db:"born"`
}

func main() {

	// Attempt to open the 'example.db' database file
	sess, err := ql.Open(settings)
	if err != nil {
		log.Fatalf("db.Open(): %q\n", err)
	}
	defer sess.Close() // Closing the session is a good practice.

	// The 'birthday' table is referenced.
	birthdayCollection := sess.Collection("birthday")

	// Any rows that might have been added between the creation of
	// the table and the execution of this function are removed.
	err = birthdayCollection.Truncate()
	if err != nil {
		log.Fatalf("Truncate(): %q\n", err)
	}

	// Three rows are inserted into the 'Birthday' table.
	birthdayCollection.Insert(Birthday{
		Name: "Hayao Miyazaki",
		Born: time.Date(1941, time.January, 5, 0, 0, 0, 0, time.Local),
	})

	birthdayCollection.Insert(Birthday{
		Name: "Nobuo Uematsu",
		Born: time.Date(1959, time.March, 21, 0, 0, 0, 0, time.Local),
	})

	birthdayCollection.Insert(Birthday{
		Name: "Hironobu Sakaguchi",
		Born: time.Date(1962, time.November, 25, 0, 0, 0, 0, time.Local),
	})

	// The database is queried for the rows inserted.
	res := birthdayCollection.Find()

	// The 'birthdays' variable is filled with the results found.
	var birthdays []Birthday

	err = res.All(&birthdays)
	if err != nil {
		log.Fatalf("res.All(): %q\n", err)
	}

	// The 'birthdays' variable is printed to stdout.
	for _, birthday := range birthday {
		fmt.Printf("%s was born in %s.\n",
			birthday.Name,
			birthday.Born.Format("January 2, 2006"),
		)
	}
}

Compile the example and run it:

go run example.go

The output will be:

Hayao Miyazaki was born in January 5, 1941.
Nobuo Uematsu was born in March 21, 1959.
Hironobu Sakaguchi was born in November 25, 1962.

Adapter particularities

SQL Builder

You can use the SQL builder for any complex SQL query:

q := b.SQL().Select(
    "p.id",
    "p.title AD publication_title",
    "a.name AS artist_name",
  ).From("artists AS a", "publication AS p").
  Where("a.id = p.author_id")

var publications []Publication
if err = q.All(&publications); err != nil {
  log.Fatal(err)
}

Helper functions

Use db.Func to escape function names and arguments:

res = sess.Find().Select(db.Func("DISTINCT", "name"))

Use the db.Raw() function for strings that have to be interpreted literally:

res = sess.Find().Select(db.Raw("DISTINCT(name)"))

db.Raw can also be used as a condition argument, similarly to db.Cond.

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