在Go中控制指针

I am trying to iterate through rows after it does a query to a database but I'm having trouble iterating through it a second time to find the females.

I believe this is because of the fact that after it iterates through rows printing out the men, the pointer is left at the end and can't go back.

rows2, rowErr :=db.Query("SELECT GIVENNAME,gender, count(givenname) as Frequency from people group by givenname order by givenname asc")

for rows2.Next() {
    nextErr := rows2.Scan(&givenName,&gender, &frequency)
    if nextErr != nil{
        log.Fatal(nextErr.Error())
    }
    if gender == "male" {
        fmt.Println(givenName, gender, frequency)
    }
}
fmt.Println("")
for rows2.Next() {
    nextErr := rows2.Scan(&givenName,&gender, &frequency)
    if nextErr != nil{
        log.Fatal(nextErr.Error())
    }
    if gender == "female" {
        fmt.Println(givenName, gender, frequency)
    }
}

How can I put the pointer at the beginning again? Or will I have to do another query?

You can't 'rollback' a pointer to a previous value, hence you have to use another (temporary) var which you use to iterate.

rows2, rowErr := db.Query("SELECT GIVENNAME, gender, count(givenname) as Frequency from people group by givenname order by givenname asc")

var list1, list2 MyPeopleStruct 
temp := rows2

for temp.Next() {
    nextErr := rows2.Scan(&givenName,&gender, &frequency)
    if nextErr != nil{
        log.Fatal(nextErr.Error())
    }

    if gender == "male" {
        fmt.Println(givenName, gender, frequency)
    }
}

fmt.Println("")

temp = rows2 // reinitialise it to the actual value you need

for temp.Next() {
    nextErr := rows2.Scan(&givenName,&gender, &frequency)
    if nextErr != nil{
        log.Fatal(nextErr.Error())
    }

    if gender == "female" {
        fmt.Println(givenName, gender, frequency)
    }
}

Anyway, why do you even need to make two different for loops?

Can't you do everything using only one? like:

type MyPeopleStruct struct{
    Gender string
    Name string
    Frequency int
}

rows2, rowErr := db.Query("SELECT GIVENNAME, gender, count(givenname) as Frequency from people group by givenname order by givenname asc")

var listM, listF []MyPeopleStruct

temp := rows2

for temp.Next() {
    nextErr := rows2.Scan(&givenName,&gender, &frequency)
    if nextErr != nil{
        log.Fatal(nextErr.Error())
    }

    if gender == "male" {
        fmt.Println(givenName, gender, frequency)
        listM = append(listM, MyPeopleStruct{gender,givenName,frequency})
    }

    if gender == "female" {
        fmt.Println(givenName, gender, frequency)
        listF = append(listF, MyPeopleStruct{gender,givenName,frequency})
    }
}

// Use listM and listF