Mysql 如何实现多张无关联表查询数据并分页

mysql 多张无关联表查询数据并分页

功能需求

在三张没有主外键关联的表中取出自己想要的数据，并且分页。

数据库表结构

水果表：

坚果表：

 

饮料表：

数据库随便建的，重在方法。

主要使用union all 操作符

union all 操作符用于合并两个或多个 select 语句的结果集。

请注意，union all内部的 select 语句必须拥有相同数量的列。列也必须拥有相似的数据类型。同时，每条 select 语句中的列的顺序必须相同 ; 另外，union all结果集中的列名总是等于 union all中第一个 select 语句中的列名。

// 详细sql语句
select * from
(
	(select fid,fname,price,type from fruits)
	union all
	(select nid,name,price,6 as type from nut)
	union all
	(select did,dname,price,7 as type from drinks)
	
) as fnd limit 0,10     -----fnd为表的别名

最终结果

mysql多表联合查询时出现的分页问题的解决

mysql一对多分页问题

部门表：tbl_dept

员工表：tbl_emp

数据库sql文件

 
create database /*!32312 if not exists*/`ssm-crud` /*!40100 default character set utf8 */;
 
use `ssm-crud`;
 
/*table structure for table `tbl_dept` */
 
drop table if exists `tbl_dept`;
 
create table `tbl_dept` (
  `dept_id` int(11) not null auto_increment,
  `dept_name` varchar(255) default null,
  primary key (`dept_id`)
) engine=innodb auto_increment=8 default charset=utf8;
 
/*data for the table `tbl_dept` */
 
insert  into `tbl_dept`(`dept_id`,`dept_name`) values 
(1,'技术部'),
(2,'业务部'),
(6,'销售部'),
(7,'人事部');
 
/*table structure for table `tbl_emp` */
 
drop table if exists `tbl_emp`;
 
create table `tbl_emp` (
  `emp_id` int(11) not null auto_increment,
  `emp_name` varchar(255) default null,
  `emp_gender` char(1) default null,
  `emp_email` varchar(255) default null,
  `d_id` int(11) default null,
  primary key (`emp_id`),
  key `fk_tbl_emp` (`d_id`),
  constraint `fk_tbl_emp` foreign key (`d_id`) references `tbl_dept` (`dept_id`)
) engine=innodb auto_increment=14 default charset=utf8;
 
/*data for the table `tbl_emp` */
 
insert  into `tbl_emp`(`emp_id`,`emp_name`,`emp_gender`,`emp_email`,`d_id`) values 
(1,'xiaoshen','2',null,6),
(4,'晓明','1',null,1),
(5,'xiaohong','2',null,2),
(6,'xiaohei','2',null,6),
(7,'xiaozhang','1',null,1),
(8,'xiaogao','1',null,1),
(9,'xiaohua','1',null,1),
(10,'xiaoyan','2',null,1),
(11,'xiaohai','2',null,2),
(12,'xiaoqiang','1',null,6),
(13,'xiaoqi','2',null,7);

分页错误写法(主查询员工表)

select * from tbl_emp e
left join 
tbl_dept d
 
on d.dept_id  = e.d_id
 
limit 1,10

使用子查询方式解决问题

select
        *
    from
     (
       select
       *
        from
        tbl_emp e
        left join 
    tbl_dept d
        on d.dept_id  = e.d_id
        
        group by e.d_id
        limit 1,10
 
     ) e
 
      left join tbl_dept d
        on d.dept_id  = e.d_id

下面代码与之无关 仅为备份

select
        ft.id,
        ft.partner_id as partnerid,
        ft.code ,
        ft.end_update_date as  endupdatedate,
        ft.name ,
        ft.type ,
        ft.area ,
        ft.is_default as  isdefault,
        fp.id fpid,
        fp.shop_id as fpshopid  ,
        fp.provice_id as fpproviceid ,
        fp.provice_name as fpprovicename ,
        fp.start_num  as fpstartnum ,
        fp.start_fee  as fpstartfee ,
        fp.increase_num as fpincreasenum ,
        fp.increase_fee as fpincreasefee ,
        fp.code as fpcode ,
        fp.provice_text as  fpprovicetext ,
        fp.template_id as fptemplateid
    from
     (
       select
        f.id,
        f.partner_id ,
        f.code ,
        f.end_update_date  ,
        f.name ,
        f.type ,
        f.area ,
        f.is_default ,
        f.is_del,
        f.create_date
        from
        bus_freight_template f
        left join bus_freight_provice p
        on f.id = p.template_id
        where f.code = p.code
        and f.code = #[code]
        group by f.id
        limit #{startpage},#{pagesize}
 
     ) ft
 
      left join bus_freight_provice fp
        on ft.id = fp.template_id
    where ft.code = fp.code
      and fp.template_id is not null
      and ft.code =  #[code]
      and fp.is_del = '0'
      and ft.is_del = '0'
 
      order by ft.create_date desc

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。