Get get number of rows using sql in golang

db.go

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/lib/pq"
)

const (
    DB_USER     = "ramesh"
    DB_PASSWORD = "secret"
    DB_NAME     = "test_db"
)

func main() {
    dbinfo := fmt.Sprintf("user=%s password=%s dbname=%s sslmode=disable",
        DB_USER, DB_PASSWORD, DB_NAME)
    db, err := sql.Open("postgres", dbinfo)
    checkErr(err)
    defer db.Close()

    rows, err := db.Query("SELECT COUNT(*) as count FROM  table_name")
 	fmt.Println("Total count:",checkCount(rows))	
    checkErr(err)
}
 
func checkCount(rows *sql.Rows) (count int) {
 	for rows.Next() {
    	err:= rows.Scan(&count)
    	checkErr(err)
    }   
    return count
}

func checkErr(err error) {
    if err != nil {
        panic(err)
    }
}

Thank you!

not sure how i feel about go at the minute. between this and unmarshalling json its a bit of a pain. also attempt batch inserts into a table. F**k

also u can:
rows := db.QueryRow("you're select count....")
rows.Scan(&count)
return count

And you will not use "for" .

As @gokca suggested, this can be done in a simpler way: https://gist.github.com/agis/7e8cd4c7a20d037c01e663402fcad9d0

Actually, AFAIK, db.QueryRow("...") is the right way. db.Query() has to be avoided for DB results that return only one row. Also in the case above, it's strongly recommended to use defer rows.Close() right after receiving rows or DB connections will start leaking

@betasve What, why does Query have to be avoided for results that return only one row? I have code that is working that queries a lookup table and panics if there is more than one entry. I don't see anything in the docs to suggest that is a problem. Furthermore, the QueryRow documentation says

QueryRow executes a query that is expected to return at most one row. QueryRow always returns a non-nil value. Errors are deferred until Row's Scan method is called.

Expected to return, but not required to return. I read that to say there could be duplicates and there is no way to tell. I think it is just a convenience function.

var count int
stmt, err = db.Prepare("SELECT COUNT(*) as count FROM YourTable")
if err != nil { log.Fatal(err) }
err = stmt.QueryRow().Scan(&count)
if err != nil { log.Fatal(err) }
log.Println(count)
stmt.Close() // or use defer rows.Close(), idc

Refference:
Go database/sql tutorial

The code here by trkrameshkumar is great though if you need to use the count functions often in various situations. WIll minimize your code, and make it more readable.

Cheers

Hi guys,

I am using the function checkCount() and it works fine.
The thing is when I call it twice in a row, the second time it returns 0.

I guess rows is not reset, is there a easy way to make the method reusable ?
Sorry if it 's a dumb question, It's literally my second day with GoLang

it is very goods!