Multiple row creation with one insert query in mysql - mysql

Question

I want to insert multiple row using one insert query.
My table looks like below:
+---------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| seq_no | varchar(20) | YES | | NULL | |
| classname | varchar(20) | YES | | NULL | |
| classteacher | varchar(20) | YES | | NULL | |
| no_of_student | varchar(20) | YES | | NULL | |
| student_roll | varchar(20) | YES | | NULL | |
+---------------+-------------+------+-----+---------+-------+
Now I want to insert values in such a way that the table looks like below:
+--------+-----------+--------------+---------------+--------------+
| seq_no | classname | classteacher | no_of_student | student_roll |
+--------+-----------+--------------+---------------+--------------+
| 1 | physics | a | 02 | 01 |
| 1 | physics | a | 02 | 02 |
+--------+-----------+--------------+---------------+--------------+
where user doesn't have to put 'student_roll'.
Help me to find a way where using below kind of query one can get the above table:
insert into temp2(seq_no,classname,classteacher,no_of_student) values ('1','physics','a','02');
Here if no_of_student is 02 then row will be created with student_roll 01 and 02 sequentially.
I was thinking of this using for loop.

Answer 1

Solutions would typically include a table of numbers and insert ... select syntax.
Here is a simple solution using an explicit inline table:
insert into temp2(seq_no,classname,classteacher,no_of_student)
select 1, 'physics', 'a', 2, n
from (
select 1 n
union all select 2
union all select 3
union all select 4
union all select 5
union all select 6
union all select 7
union all select 8
union all select 9
union all select 10
) t
In MySQL 8.0, if you have a table with enough records, say other_table, you can use row_number():
insert into temp2(seq_no,classname,classteacher,no_of_student)
select 1, 'physics', 'a', 2, n
from (select row_number() over(order by rand()) n from other_table) t
where n <= :number_of_records to insert
Note: it has been commented already by RiggsFolly that the numeric-like values should be stored as numbers, not as strings. This answer assumes that. Else, you would need to cast() integer values to char, like so:
insert into ...
select '1', 'physics', 'a', '2', cast(n as char)
from ...

Answer 2

Here I have created another table named "other_table". It hold two columns "num" and "num_explain". and the table looks like below:
+-----+-------------+
| num | num_explain |
+-----+-------------+
| 02 | 01 |
| 02 | 02 |
+-----+-------------+
Then I have used the below code to get desired result:
insert into temp2(seq_no,classname,classteacher,no_of_student,student_roll) select '1','physics','a',num,num_explain from other_table where num='02';