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。
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// 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
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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
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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);
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分页错误写法(主查询员工表)
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select * from tbl_emp e
left join
tbl_dept d
on d.dept_id = e.d_id
limit 1,10
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使用子查询方式解决问题
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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
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下面代码与之无关 仅为备份
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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
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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服务器之家。
原文链接：https://blog.csdn.net/qq_38159467/article/details/85015559