改进代码var req []*Total res := db.Scopes(models.Paginate(page, pageSize)).Raw("SELECT * FROM flaws WHERE facility_id = ? "+ "UNION SELECT * FROM issues WHERE facility_id = ? "+ "UNION SELECT * FROM records WHERE facility_id = ? "+ "UNION SELECT * FROM qualities WHERE facility_id = ? "+ "UNION SELECT * FROM inspections WHERE facility_id = ?", code, code, code, code, code).Find(&req) if res.RowsAffected == 0 { resp.Code = 400 resp.Msg = "记录不存在" ctx.JSON(400, resp) return } resp.Data = req ctx.JSON(200, resp)

可以将这段代码进行重构，使其更加简洁和易读。可以使用以下方式重构：

var total []*Total 
db.Where("facility_id = ?", code).Scopes(
  models.Paginate(page, pageSize),
).Find(&total)

if len(total) == 0 {
  ctx.JSON(400, Response{
    Code:  400,
    Msg:   "记录不存在",
    Data:  nil,
  })
  return
}

ctx.JSON(200, Response{
  Code:  200,
  Msg:   "成功获取记录列表",
  Data:  total,
})

这样可以将查询语句进行简化，同时也可以将错误响应和成功响应的代码进行分离，使得代码更加易于维护。

相关问题

改进代码var req []*Total res := db.Scopes(models.Paginate(page, pageSize)).Raw("SELECT * FROM flaws WHERE facility_id = ? "+ "UNION SELECT * FROM issues WHERE facility_id = ? "+ "UNION SELECT * FROM records WHERE facility_id = ? "+ "UNION SELECT * FROM qualities WHERE facility_id = ? "+ "UNION SELECT * FROM inspections WHERE facility_id = ?", code, code, code, code, code).Find(&req)

可以尝试使用预编译语句来优化 SQL 查询性能，同时使用占位符来避免 SQL 注入攻击。改进后的代码如下所示：

stmt, err := db.DB().Prepare("SELECT * FROM flaws WHERE facility_id = ? " +
    "UNION SELECT * FROM issues WHERE facility_id = ? " +
    "UNION SELECT * FROM records WHERE facility_id = ? " +
    "UNION SELECT * FROM qualities WHERE facility_id = ? " +
    "UNION SELECT * FROM inspections WHERE facility_id = ? " +
    "LIMIT ? OFFSET ?")
if err != nil {
    // 处理错误
}
defer stmt.Close()

req := make([]*Total, 0)
offset := (page - 1) * pageSize
limit := pageSize
rows, err := stmt.Query(code, code, code, code, code, limit, offset)
if err != nil {
    // 处理错误
}
defer rows.Close()

for rows.Next() {
    var item Total
    err := rows.Scan(&item)
    if err != nil {
        // 处理错误
    }
    req = append(req, &item)
}

if err := rows.Err(); err != nil {
    // 处理错误
}

res := db.Model(&Total{}).Where("facility_id = ?", code).Count(&Total{})

// 处理结果

这里我们使用了 `db.DB().Prepare()` 方法来预编译 SQL 查询语句，并使用占位符 `?` 来代替变量，从而避免了 SQL 注入攻击。

同时，我们也将分页查询的 `LIMIT` 和 `OFFSET` 参数移到了 SQL 查询语句中，以避免使用 `Scopes()` 方法产生额外的查询开销。在查询结果时，我们使用 `stmt.Query()` 方法来执行查询，并使用 `rows.Scan()` 方法将查询结果映射到结构体中。

最后，我们使用 `db.Model().Where().Count()` 方法来查询总记录数，并将结果返回给调用者。

改进代码var req []*Total res := db.Scopes(models.Paginate(page, pageSize)).Raw("SELECT * FROM flaws WHERE facility_id = ? "+ "UNION SELECT * FROM issues WHERE facility_id = ? "+ "UNION SELECT * FROM records WHERE facility_id = ? "+ "UNION SELECT * FROM qualities WHERE facility_id = ? "+ "UNION SELECT * FROM inspections WHERE facility_id = ?", code, code, code, code, code).Find(&req)

这段代码可以优化为使用GORM的联合查询（Union）功能，避免使用Raw SQL语句。

可以尝试这样改进代码：

err := db.Where("facility_id = ?", code).
    Select("id, created_at, updated_at, field1, field2, NULL as field3, NULL as field4, NULL as field5").
    Table("flaws").
    Union(db.Where("facility_id = ?", code).
        Select("id, created_at, updated_at, field1, NULL as field2, field3, field4, NULL as field5").
        Table("issues")).
    Union(db.Where("facility_id = ?", code).
        Select("id, created_at, updated_at, field1, NULL as field2, NULL as field3, NULL as field4, field5").
        Table("records")).
    Union(db.Where("facility_id = ?", code).
        Select("id, created_at, updated_at, field1, field2, NULL as field3, NULL as field4, NULL as field5").
        Table("qualities")).
    Union(db.Where("facility_id = ?", code).
        Select("id, created_at, updated_at, field1, NULL as field2, field3, field4, field5").
        Table("inspections")).
    Order("created_at desc").
    Limit(pageSize).
    Offset((page - 1) * pageSize).
    Find(&req).Error

在这个示例中，我们使用了 `Select` 函数选择每个表中的字段，并将不需要的字段设置为 `NULL`。然后我们使用 `Union` 函数将所有查询合并到一起，并使用 `Order`、`Limit` 和 `Offset` 函数进行分页和排序。

这种方法比使用 `Raw` 函数更安全，因为它可以防止 SQL 注入攻击，并且更易于维护。