sqlx

#sqlx

sqlx is a library which provides a set of extensions on go's standard database/sql library. The sqlx versions of sql.DB, sql.TX, sql.Stmt, et al. all leave the underlying interfaces untouched, so that their interfaces are a superset on the standard ones.

Major additional concepts are:

• Marshal rows into structs (with embedded struct support), maps, and slices
• Named parameter support
• Get and Select to go quickly from query to struct/slice
• Common error handling mnemonics (eg. Execf, Execp (MustExec), and Execl)
• LoadFile for executing statements from a file

Read the usage below to see how sqlx might help you, or check out the API documentation on godoc.

install

go get github.com/jmoiron/sqlx

issues

Row headers can be ambiguous (SELECT 1 AS a, 2 AS a), and the result of Columns() can have duplicate names on queries like:

SELECT a.id, a.name, b.id, b.name FROM foos AS a JOIN foos AS b ON a.parent = b.id;

making a struct or map destination ambiguous. Use AS in your queries to give rows distinct names, rows.Scan to scan them manually, or SliceScan to get a slice of results.

usage

Below is an example which shows some common use cases for sqlx. Check sqlx_test.go for more usage.

package main

import (
    _ "github.com/lib/pq"
    "database/sql"
    "github.com/jmoiron/sqlx"
    "log"
)

var schema = `
CREATE TABLE person (
    first_name text,
    last_name text,
    email text
);

CREATE TABLE place (
    country text,
    city text NULL,
    telcode integer
)`

type Person struct {
    FirstName string `db:"first_name"`
    LastName  string `db:"last_name"`
    Email     string
}

type Place struct {
    Country string
    City    sql.NullString
    TelCode int
}

func main() {
    // this connects & tries a simple 'SELECT 1', panics on error
    // use sqlx.Open() for sql.Open() semantics
    db, err := sqlx.Connect("postgres", "user=foo dbname=bar sslmode=disable")
    if err != nil {
        log.Fatalln(err)
    }

    // exec the schema or fail; multi-statement Exec behavior varies between
    // database drivers;  pq will exec them all, sqlite3 won't, ymmv
    db.Execf(schema)
    
    tx := db.MustBegin()
    tx.Execl("INSERT INTO person (first_name, last_name, email) VALUES ($1, $2, $3)", "Jason", "Moiron", "jmoiron@jmoiron.net")
    tx.Execl("INSERT INTO person (first_name, last_name, email) VALUES ($1, $2, $3)", "John", "Doe", "johndoeDNE@gmail.net")
    tx.Execl("INSERT INTO place (country, city, telcode) VALUES ($1, $2, $3)", "United States", "New York", "1")
    tx.Execl("INSERT INTO place (country, telcode) VALUES ($1, $2)", "Hong Kong", "852")
    tx.Execl("INSERT INTO place (country, telcode) VALUES ($1, $2)", "Singapore", "65")
    // Named queries can use structs, so if you have an existing struct (i.e. person := &Person{}) that you have populated, you can pass it in as &person
    tx.NamedExec("INSERT INTO person (first_name, last_name, email) VALUES (:first_name, :last_name, :email)", &Person{"Jane", "Citizen", "jane.citzen@example.com"})
    tx.Commit()

    // Query the database, storing results in a []Person (wrapped in []interface{})
    people := []Person{}
    db.Select(&people, "SELECT * FROM person ORDER BY first_name ASC")
    jason, john := people[0], people[1]

    fmt.Printf("%#v\n%#v", jason, john)
    // Person{FirstName:"Jason", LastName:"Moiron", Email:"jmoiron@jmoiron.net"}
    // Person{FirstName:"John", LastName:"Doe", Email:"johndoeDNE@gmail.net"}

    // You can also get a single result, a la QueryRow
    jason = Person{}
    err = db.Get(&jason, "SELECT * FROM person WHERE first_name=$1", "Jason")
    fmt.Printf("%#v\n", jason)
    // Person{FirstName:"Jason", LastName:"Moiron", Email:"jmoiron@jmoiron.net"}

    // if you have null fields and use SELECT *, you must use sql.Null* in your struct
    places := []Place{}
    err := db.Select(&places, "SELECT * FROM place ORDER BY telcode ASC")
    if err != nil {
        fmt.Printf(err)
        return
    }
    usa, singsing, honkers = places[0], places[1], places[2]
    
    fmt.Printf("%#v\n%#v\n%#v\n", usa, singsing, honkers)
    // Place{Country:"United States", City:sql.NullString{String:"New York", Valid:true}, TelCode:1}
    // Place{Country:"Singapore", City:sql.NullString{String:"", Valid:false}, TelCode:65}
    // Place{Country:"Hong Kong", City:sql.NullString{String:"", Valid:false}, TelCode:852}

    // Loop through rows using only one struct
    place := Place{}
    rows, err := db.Queryx("SELECT * FROM place")
    for rows.Next() {
        err := rows.StructScan(&place)
        if err != nil {
            log.Fataln(err)
        } 
        fmt.Printf("%#v\n", place)
    }
    // Place{Country:"United States", City:sql.NullString{String:"New York", Valid:true}, TelCode:1}
    // Place{Country:"Hong Kong", City:sql.NullString{String:"", Valid:false}, TelCode:852}
    // Place{Country:"Singapore", City:sql.NullString{String:"", Valid:false}, TelCode:65}

    // Named queries, using `:name` as the bindvar.  Automatic bindvar support
    // which takes into account the dbtype based on the driverName on sqlx.Open/Connect
    _, err = db.NamedExecMap(`INSERT INTO person (first_name,last_name,email) VALUES (:first,:last,:email)`, 
        map[string]interface{}{
            "first": "Bin",
            "last": "Smuth",
            "email": "bensmith@allblacks.nz",
    })

    // Selects Mr. Smith from the database
    rows, err := db.NamedQueryMap(`SELECT * FROM person WHERE first_name=:fn`, map[string]interface{}{"fn": "Bin"})

    // Named queries can also use structs.  Their bind names follow the same rules
    // as the name -> db mapping, so struct fields are lowercased and the `db` tag
    // is taken into consideration.
    rows, err := db.NamedQuery(`SELECT * FROM person WHERE first_name=:first_name`, jason)
}

embedded structs

Structs which do not implement the sql.Scanner interface will be inspected and their fields used as possible targets for a scan. This includes embedded and non-embedded structs.

Go makes 'ambiguous selectors' a compile time error, but does not make structs with possible ambiguous selectors errors. Sqlx will decide which field to use on a struct based on a breadth first search of the struct and any structs it contains or embeds, as specified by the order of the fields as accessible by reflect, which generally means in source-order.