GO DB.Query用法及代碼示例

GO語言"database/sql"包中"DB.Query"類型的用法及代碼示例。

用法:

func(db *DB) Query(query string, args ...any)(*Rows, error)

Query 執行返回行的查詢，通常是 SELECT。 args 用於查詢中的任何占位符參數。

查詢在內部使用 context.Background；要指定上下文，請使用QueryContext

示例(多個結果集)：

package main

import (
    "context"
    "database/sql"
    "log"
)

var (
    ctx context.Context
    db  *sql.DB
)

func main() {
    age := 27
    q := `
create temp table uid (id bigint); -- Create temp table for queries.
insert into uid
select id from users where age < ?; -- Populate temp table.

-- First result set.
select
    users.id, name
from
    users
    join uid on users.id = uid.id
;

-- Second result set.
select 
    ur.user, ur.role
from
    user_roles as ur
    join uid on uid.id = ur.user
;
    `
    rows, err := db.Query(q, age)
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()

    for rows.Next() {
        var (
            id   int64
            name string
        )
        if err := rows.Scan(&id, &name); err != nil {
            log.Fatal(err)
        }
        log.Printf("id %d name is %s\n", id, name)
    }
    if !rows.NextResultSet() {
        log.Fatalf("expected more result sets: %v", rows.Err())
    }
    var roleMap = map[int64]string{
        1: "user",
        2: "admin",
        3: "gopher",
    }
    for rows.Next() {
        var (
            id   int64
            role int64
        )
        if err := rows.Scan(&id, &role); err != nil {
            log.Fatal(err)
        }
        log.Printf("id %d has role %s\n", id, roleMap[role])
    }
    if err := rows.Err(); err != nil {
        log.Fatal(err)
    }
}

相關用法

注：本文由純淨天空篩選整理自golang.google.cn大神的英文原創作品 DB.Query。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。