核心
对两张表的关联字段左右两边同时加上分隔符，然后使用instr()函数判断是否存在
instr(','||class_student.student_id||',' , ','||student.student_id||',') > 0
数据
student(学生表)
| 学生编号 | 学生姓名 |
|---|---|
| 1 | 张三 |
| 2 | 李四 |
| 3 | 王五 |
class_student(班级学生关系表)
| 班级编号 | 学生编号 |
|---|---|
| 1 | 1,2 |
| 2 | 3 |
| 3 | 4 |
应用
1. 标题查询学生所在班级（一个字段存多个ID(以逗号","分割),并用该字段与其他表的ID关联）
with student as(--学生表
select '1' student_id,'张三' student_name from dual union
select '2' student_id,'李四' student_name from dual union
select '3' student_id,'王五' student_name from dual
),class_student as(--班级学生关系表
select '1' as class_id,'1,2' student_id from dual union
select '2' as class_id,'3' student_id from dual union
select '3' as class_id,'4' student_id from dual
)select
student.student_id,
class_student.class_id
from student
join class_student on instr(','||class_student.student_id||',' , ','||student.student_id||',') > 0
结果展示
| 学生编号 | 班级编号 |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
2. 获取每个班级学生对应姓名（将存多个ID(以逗号","分割)的字段转化成对应中文含义）
with student as(--学生表
select '1' student_id,'张三' student_name from dual union
select '2' student_id,'李四' student_name from dual union
select '3' student_id,'王五' student_name from dual
),class_student as(--班级学生关系表
select '1' as class_id,'1,2' student_id from dual union
select '2' as class_id,'3' student_id from dual union
select '3' as class_id,'4' student_id from dual
)select
class_student.class_id,
(select listagg(student.student_name, ',') within group(order by student.student_id) from student where instr(','||class_student.student_id||',' , ','||student.student_id||',') > 0) student_name
from class_student
结果展示
| 班级编号 | 学生姓名 |
|---|---|
| 1 | 张三,李四 |
| 2 | 王五 |
| 3 |