sql: expected 3 destination arguments in Scan, not 1 in Golang - sql

Question

I am writing a generic code to query data from any RDS table. I have gone through many StackOverflow answers but none of it worked for me. I have gone through below links:-
panic: sql: expected 1 destination arguments in Scan, not <number> golang, pq, sql
How to query any table of RDS using Golang SDK
My first code is
package main
import (
"fmt"
)
type BA_Client struct {
ClientId int `json:ClientId;"`
CompanyName string `json:CompanyName;"`
CreateDate string `json:CreateDate;"`
}
func main() {
conn, _ := getConnection() // Det database connection
query := `select * from IMBookingApp.dbo.BA_Client
ORDER BY
ClientId ASC
OFFSET 56 ROWS
FETCH NEXT 10 ROWS ONLY ;`
var p []byte
err := conn.QueryRow(query).Scan(&p)
if err != nil {
fmt.Println("Error1", err)
}
fmt.Println("Data:", p)
var m BA_Client
err = json.Unmarshal(p, &m)
if err != nil {
fmt.Println("Error2", err)
}
}
My second code is
conn, _ := getConnection()
query := `select * from IMBookingApp.dbo.BA_Client__c
ORDER BY
ClientId__c ASC
OFFSET 56 ROWS
FETCH NEXT 10 ROWS ONLY ;`
rows, err := conn.Query(query)
if err != nil {
fmt.Println("Error:")
log.Fatal(err)
}
println("rows", rows)
defer rows.Close()
columns, err := rows.Columns()
fmt.Println("columns", columns)
if err != nil {
panic(err)
}
for rows.Next() {
receiver := make([]*string, len(columns))
err := rows.Scan(&receiver )
if err != nil {
fmt.Println("Error reading rows: " + err.Error())
}
fmt.Println("Data:", p)
fmt.Println("receiver", receiver)
}
With both the codes, I am getting the same error as below
sql: expected 3 destination arguments in Scan, not 1
Can it be because I am using SQL Server and not MySQL? Appreciate if anyone can help me to find the issue.

Answer 1

When you want to use a slice of inputs for your row scan, use the variadic 3-dots notation ... to convert the slice into individual parameters, like so:
err := rows.Scan(receiver...)
Your (three in this case) columns, using the variadic arguments will effectively expand like so:
// len(receiver) == 3
err := rows.Scan(receiver[0], receiver[1], receiver[2])
EDIT:
SQL Scan method parameter values must be of type interface{}. So we need an intermediate slice. For example:
is := make([]interface{}, len(receiver))
for i := range is {
is[i] = receiver[i]
// each is[i] will be of type interface{} - compatible with Scan()
// using the underlying concrete `*string` values from `receiver`
}
// ...
err := rows.Scan(is...)
// `receiver` will contain the actual `*string` typed items

Answer 2

try this (no ampersand in front of receiver) for second example:
err := rows.Scan(receiver)
receiver and *string are already a reference types. No need to add another reference to it.

Answer 3

specific field table
query := `select * from IMBookingApp.dbo.BA_Client__c
ORDER BY
ClientId__c ASC
OFFSET 56 ROWS
FETCH NEXT 10 ROWS ONLY ;`
change to
query := `select ClientId, CompanyName, CreateDate from IMBookingApp.dbo.BA_Client__c
ORDER BY
ClientId__c ASC
OFFSET 56 ROWS
FETCH NEXT 10 ROWS ONLY ;`