Querying Multiple Rows

Ko'p qatorni so'rash

Bir nechta qator qaytaradigan SELECT uchun db.Query ishlatiladi. Natija — *sql.Rows, uni for rows.Next() bilan qatorma-qator o'qiysiz ("Reading Files Line by Line" darsidagi bufio.Scannerga o'xshash naqsh).

example.go

rows, err := db.Query("SELECT id, name, age FROM users")
if err != nil {
	fmt.Println("xato:", err)
	return
}
defer rows.Close() // HAR DOIM yoping, aks holda ulanish "sizib qoladi"!

for rows.Next() {
	var id, age int64
	var name string
	if err := rows.Scan(&id, &name, &age); err != nil {
		fmt.Println("scan xatosi:", err)
		return
	}
	fmt.Println(id, name, age)
}

rows.Scan(&id, &name, &age) — joriy qatorning ustunlarini, aynan SELECT'dagi tartibda, berilgan o'zgaruvchilarga pointer orqali yozadi. defer rows.Close() — bu darsning eng muhim qoidasi: uni unutish, ulanishni butun sikl davomida band qilib qo'yadi ("connection leak"), va oxir-oqibat ulanishlar tugab qolishi mumkin.

>_ Exercise

Barcha foydalanuvchilarni o'qib chiqing.

•db.Query bilan "SELECT id, name, age FROM users" ni bajaring
•for rows.Next() bilan har bir qatorni Scan qiling
•har birini "id name age" ko'rinishida chop eting

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Key Takeaway

Key Takeaway:

db.Query + rows.Next()/Scan() — ko'p qatorli natijalarni o'qishning standart naqshi; rows.Close()ni hech qachon unutmang.

NEXT UP

Querying a Single Row

OUTPUT

$ go run main.go
Kodingizni ishga tushiring