Golang sql named parameter query

Question

I am trying to use named parameter query in golang as follows:

stmt, err := db.Prepare("insert into users(name, email) values(@name, @email)")
if err != nil {
    //error handling
}

res, err := stmt.Exec(sql.Named("name", name), sql.Named("email", email))

if err != nil {
        //error: sql: expected 0 arguments, got 2 
}

I get the following error: "sql: expected 0 arguments, got 2".

What is correct way to write this query?

Answer 1

Use sql params by name for Oracle, Postgre, Mysql ....

/*Examples:
  ParamReplacingMode = 0  // no replacing params
  isql:=InitSql(db,"SELECT * FROM table WHERE price+vat>:Sum and country=:C") // by Oracle
  Params(isql,
    ":C", "USA",                    // the order for Params is not bound, you can add params any order, case insensitive
    ":Sum", 130.5)
  res,err:= SqlQuery(isql)          // result: db.Query("SELECT * FROM table WHERE price+vat>:Sum and country=:C", 130.5,"USA")
  if err!=nil {
    fmt.Println("Error:"+fmt.Sprint(err)+SqlStr(isql))
  }
or
  ParamReplacingMode = 1  // MySQL  - replacing params to "?"
  isql:=InitSql(db,"SELECT * FROM table WHERE price+vat>:Sum and country=:C") // by Oracle convert to Mysql
  Params(isql,
    ":C", "USA",                    // the order for Params is not bound, you can add params any order, case insensitive
    ":Sum", 130.5)
  res,err:= SqlQuery(isql)          // result: db.Query("SELECT * FROM table WHERE price+vat>? and country=?", 130.5,"USA") //replacing params to "?"
or
  ParamReplacingMode = 0  //no replacing params
  isql:=InitSql(db,"SELECT * FROM table WHERE price+vat>$1 and country=$2")   // by Postgre
  AddParam(isql,"$1", 130.5)        // AddParam() is the same as Params(), but only for 1 param
  AddParam(isql,"$2", "USA")        // the order for AddParams is not bound, you can add params any order
  res,err:= SqlQuery(isql)          // result: db.Query("SELECT * FROM table WHERE price+vat>$1 and country=$2", 130.5,"USA")
or
  ParamReplacingMode = 2  // mode Oracle to Postgre, replacing params to <$Number>
  isql:=InitSql(db,"SELECT * FROM table WHERE price+vat>:Sum and country=:C") // by Oracle convert to Postgre
  AddParam(isql,":C","USA")        // AddParam()) is the same as Params(), but only for 1 param
  AddParam(isql,":Sum",130.5)
  res,err:= SqlQuery(isql)         // result: db.Query("SELECT * FROM table WHERE price+vat>$1 and country=$2", 130.5,"USA")

SqlExec() is similar as SqlQuery(), but call db.Exec(...)

  Example , add NULL value:
  isql:=InitSql(db,"INSERT INTO table (id, name) VALUES (:ID,:Name)" )
  Params(isql, ":ID", 1, ":Name", nil)     //NULL
  res,err:= SqlExec(isql)
  if err!=nil {
    fmt.Println("Error:"+fmt.Sprint(err)+SqlStr(isql))
  }
*/

type (
    TisqlMode int32
    TisqlAt   struct {
        ParamName string
        Pos       int
        ParamVal  any
    }

    Tisql struct {
        Sql       string
        ResultSql string
        DB        *sql.DB
        Params    map[string]any
        At        []TisqlAt
    }
)

const (
    Oracle  TisqlMode = iota //0, no replacing params
    Mysql                    //1, "SELECT * FROM table WHERE price+vat>:Sum and country=:C" -> db.Query("SELECT * FROM table WHERE price+vat>? and country=?", 130.5,"USA")
    Postgre                  //2, "SELECT * FROM table WHERE price+vat>:Sum and country=:C" -> db.Query("SELECT * FROM table WHERE price+vat>$1 and country=$2", 130.5,"USA")
)

var ParamReplacingMode TisqlMode = -1 //-1 = unknown,  0 = no replacing params,  1 = to MySql,  2 = to Postgre

func indexAt(pStr, pSubStr string, pFrom ...int) int { //Index from position
    pos := 0
    if len(pFrom) > 0 {
        pos = pFrom[0]
    }
    if pos >= len(pStr) {
        return -1
    }
    if pos < 0 {
        pos = 0
    }
    idx := strings.Index(pStr[pos:], pSubStr)
    if idx > -1 {
        idx += pos
    }
    return idx
}
func InitSql(db *sql.DB, sql string) *Tisql {
    if ParamReplacingMode < 0 { // unknow
        _, err := db.Exec("?")
        if err != nil {
            s := strings.ToLower(fmt.Sprint(err))
            if indexAt(s, "mysql") > 0 {
                ParamReplacingMode = 1
            } else {
                ParamReplacingMode = 0
            }
        }
    }
    var isql Tisql
    isql.Sql = sql
    isql.DB = db
    isql.Params = make(map[string]any)
    return &isql
}

func AddParam(isql *Tisql, pParam string, pValue any) bool {
    pParam = strings.TrimSpace(pParam)
    if len(pParam) > 1 {
        isql.Params[pParam] = pValue
        return true
    }
    return false
}

func Params(isql *Tisql, pParam ...any) (added int) { //https://stackoverflow.com/questions/6996704/how-to-check-variable-type-at-runtime-in-go-language
    c := len(pParam)
    if c%2 == 1 {
        c = c - 1
    }
    cnt, i, s := 0, 0, ""
    for i < c {
        s = strings.TrimSpace(pParam[i].(string))
        if len(s) > 1 {
            isql.Params[s] = pParam[i+1]
            cnt++
        }
        i += 2
    }
    return cnt
}

func paramOrder(isql *Tisql, pCheckParamCount bool) error {
    var at TisqlAt
    isql.ResultSql = isql.Sql
    t := ""
    b := strings.ToLower(isql.Sql) + " "
    mMode := ParamReplacingMode
    var p, p1, p2 int
    for name, v := range isql.Params {
        p1 = 0
        for p1 >= 0 {
            p = indexAt(b, strings.ToLower(name), p1)
            if p < 0 {
                p1 = -1
                continue
            } else {
                p2 = p + len(name)
                t = b[p2 : p2+1] //char after param
                if indexAt(" :,;!?%$<>^*+-/()[]{}=|'`\"\r\n\t", t) < 0 {
                    p1 = p + 1
                    continue
                }
                p1 = -1
            }
        }
        if p >= 0 {
            at.Pos = p
            at.ParamVal = v
            at.ParamName = name
            isql.At = append(isql.At, at)
        }
    }
    if pCheckParamCount && len(isql.At) != len(isql.Params) {
        return fmt.Errorf("Different count of params %d / %d", len(isql.At), len(isql.Params))
    }
    if len(isql.At) > 1 {
        sort.Slice(isql.At,
            func(i, j int) bool {
                return isql.At[i].Pos < isql.At[j].Pos
            })
    }
    mLen := len(isql.Sql)
    switch mMode {
    case 1: //to Mysql
        {
            p1, p2, s := 0, 0, ""
            for _, at := range isql.At {
                p2 = at.Pos
                if p2 >= 0 && p2 <= mLen {
                    if p2 > p1 {
                        s += isql.Sql[p1:p2] + "?"
                    }
                    p1 = p2 + len(at.ParamName)
                }
            }
            if p1 < len(isql.Sql) {
                s += isql.Sql[p1:len(isql.Sql)]
            }
            isql.ResultSql = s
        }
    case 2: //to Postgre
        {
            p1, p2, s := 0, 0, ""
            for i, at := range isql.At {
                p2 = at.Pos
                if p2 >= 0 && p2 <= mLen {
                    if p2 > p1 {
                        s += isql.Sql[p1:p2] + "$" + fmt.Sprint(i+1)
                    }
                    p1 = p2 + len(at.ParamName)
                }
            }
            if p1 < len(isql.Sql) {
                s += isql.Sql[p1:len(isql.Sql)]
            }
            isql.ResultSql = s
        }
    }
    return nil
}

func ParamsStr(isql *Tisql) string {
    s := ""
    for i, at := range isql.At {
        s += "[" + fmt.Sprint(i+1) + ". " + at.ParamName + "=\"" + fmt.Sprint(at.ParamVal) + "\"]"
    }
    return s
}
func SqlStr(isql *Tisql) string {
    s := " SQL:[" + isql.ResultSql + "]"
    if len(isql.At) > 0 {
        s += " Params:" + ParamsStr(isql)
    }
    return s
}

func SqlExec(isql *Tisql, opt ...bool) (sql.Result, error) {
    checkParamCount := false
    if len(opt) > 0 {
        checkParamCount = opt[0]
    }
    err := paramOrder(isql, checkParamCount)
    if err != nil {
        return nil, err
    }
    mLen := len(isql.At)
    mVal := make([]any, mLen)
    for i := range mVal {
        mVal[i] = isql.At[i].ParamVal
    }
    return isql.DB.Exec(isql.ResultSql, mVal...)
}

func SqlQuery(isql *Tisql, opt ...bool) (*sql.Rows, error) {
    checkParamCount := false
    if len(opt) > 0 {
        checkParamCount = opt[0]
    }
    err := paramOrder(isql, checkParamCount)
    if err != nil {
        return nil, err
    }
    mLen := len(isql.At)
    mVal := make([]any, mLen)
    for i := range mVal {
        mVal[i] = isql.At[i].ParamVal
    }
    return isql.DB.Query(isql.ResultSql, mVal...)
}

Answer 2

Go needs to support every kind of SQL server - and not all SQL servers support named parameters. The servers that do support them do it with a variety of quirks and "gotchas". But they all support positional parameters just fine.

However there is an open issue for it for the mysql-driver: https://github.com/go-sql-driver/mysql/issues/561