GORM SELECT * FROM table1 WHERE type = '图片'UNIONSELECT * FROM table2 WHERE type = '图片'UNIONSELECT * FROM table3 WHERE type = '图片'UNIONSELECT * FROM table4 WHERE type = '图片'UNIONSELECT * FROM table5 WHERE type = '图片';

以上 SQL 语句是一个查询语句，目的是从 5 个表中选出 type 字段为 '图片' 的所有行，并将它们合并成一个结果集。其中使用了 UNION 运算符将多个 SELECT 语句的结果合并。这里的 * 表示选取所有列。GORM 是一个 Go 语言 ORM 框架，可以通过该框架进行数据库操作，包括查询、插入、更新、删除等。在 GORM 中，可以使用 Raw 方法执行原始 SQL 语句，例如：

db.Raw("SELECT * FROM table1 WHERE type = ? UNION SELECT * FROM table2 WHERE type = ? UNION SELECT * FROM table3 WHERE type = ? UNION SELECT * FROM table4 WHERE type = ? UNION SELECT * FROM table5 WHERE type = ?", "图片", "图片", "图片", "图片", "图片").Scan(&result)

其中，? 是占位符，用于占据 SQL 语句中的参数位置，Scan 方法用于将查询结果转换为指定类型的数据结构。

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)

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。

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)

这段代码可以进行一些改进来提高效率和可读性。首先，可以使用更具可读性的命名来使代码更易于理解。其次，可以使用`ErrRecordNotFound`错误来处理记录不存在的情况，这样代码更易于维护和扩展。最后，可以使用`db.Table`将SQL查询转换为更清晰的代码。

下面是改进后的代码示例：

var (
    records []*Total
    err     error
)

err = db.Table("flaws").Where("facility_id = ?", code).Find(&records).Error
if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
    resp.Code = 500
    resp.Msg = "查询失败"
    ctx.JSON(500, resp)
    return
}

err = db.Table("issues").Where("facility_id = ?", code).Find(&records).Error
if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
    resp.Code = 500
    resp.Msg = "查询失败"
    ctx.JSON(500, resp)
    return
}

err = db.Table("records").Where("facility_id = ?", code).Find(&records).Error
if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
    resp.Code = 500
    resp.Msg = "查询失败"
    ctx.JSON(500, resp)
    return
}

err = db.Table("qualities").Where("facility_id = ?", code).Find(&records).Error
if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
    resp.Code = 500
    resp.Msg = "查询失败"
    ctx.JSON(500, resp)
    return
}

err = db.Table("inspections").Where("facility_id = ?", code).Find(&records).Error
if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
    resp.Code = 500
    resp.Msg = "查询失败"
    ctx.JSON(500, resp)
    return
}

if len(records) == 0 {
    resp.Code = 400
    resp.Msg = "记录不存在"
    ctx.JSON(400, resp)
    return
}

resp.Data = records
ctx.JSON(200, resp)

通过这些改进，代码变得更加易于理解和维护，并且可以更清晰地处理错误和异常情况。