Microsoft SQL server adapter

The mssql adapter for SQL Server wraps the github.com/denisenkom/go-mssqldb driver written by denisenkom.

Here you'll learn about the particularities of the SQL server adapter. 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/v4/adapter/mssql

Setup

Database Session

Import the mssql package into your application:

// main.go
package main

import (
  "github.com/upper/db/v4/adapter/mssql"
)

Define the mssql.ConnectionURL{} struct:

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

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

settings = mssql.ConnectionURL{
  ...
}

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

The mssql.ParseURL() function is also provided in case you need to convert the DSN into a mssql.ConnectionURL:

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

Common Database Operations

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
CREATE TABLE [birthdays] (
  id BIGINT PRIMARY KEY NOT NULL IDENTITY(1,1),
  name NVARCHAR(50),
  born DATETIME,
  born_ut BIGINT
);

The sqlcmd command line tool is used to run the statements in the upperio_tests database:

sqlcmd -U upperio -P upperio -i example.sql

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

// example.go

package main

import (
  "fmt"
  "log"
  "time"

  "github.com/upper/db/v4/adapter/mssql"
)

var settings = mssql.ConnectionURL{
  Database: `upperio_tests`,  // Database name
  Host:     `localhost,`      // Server IP or name
  User:     `upperio`,        // Username
  Password: `upperio`,        // Password
}

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() {

  // The database connection is attempted.
  sess, err := mssql.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 birthdays {
    fmt.Printf("%s was born in %s.\n",
      birthday.Name,
      birthday.Born.Format("January 2, 2006"),
    )
  }
}

The Go file is compiled and executed using go run:

go run example.go

The output consists of three rows including names and birthdates:

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

Specifications

JSON Types

You can save and retrieve data when using JSON types. If you want to try this out, make sure the column type is json and the field type is mssql.JSON:

import (
  ...
  "github.com/upper/db/v4/adapter/mssql"
  ...
)

type Person struct {
  ...
  Properties  mssql.JSON  `db:"properties"`
  Meta        mssql.JSON  `db:"meta"`
}

JSON types area supported on SQL Server 2016+.

SQL Builder

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

q := sess.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)
}

Identity Columns

If you want tables to generate a unique number automatically whenever a new record is inserted, you can use auto-incremental keys. In this case, the column must be defined as IDENTITY(1, 1).

In order for the ID to be returned by db.Collection.Insert(), the IDENTITY column must be set as PRIMARY KEY too.

CREATE TABLE foo(
  id BIGINT PRIMARY KEY NOT NULL IDENTITY(1,1),
  title NVARCHAR(50)
);

Remember to use omitempty to specify that the ID field should be ignored if it has an empty value:

type Foo struct {
  ID    int64   `db:"id,omitempty"`
  Title string  `db:"title"`
}

Otherwise, an error will be returned.

Escape Sequences

There might be characters that cannot be typed in the context you're working, or else would have an undesired interpretation. Through db.Func you can encode the syntactic entities that cannot be directly represented by the alphabet:

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

On the other hand, you can use the db.Raw function so a given value is taken 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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