C# sql insert data from one table to another

Question

4.33/5 (3 votes)

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I have two tables in my database.
students_table and student_details table.
I need to get all student names from students_table and insert them in student_details table if they already don't exist. how can this be done?
Select Name from students_table,
for each Name if it does not already exist in student_details table than insert it.
So, i populate a data table with select query and get all the values, how do i insert them in student_details table.

Posted 23-Oct-13 9:47am

Mubshir

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4 solutions

Solution 1

You should be copying IDs rather than names. Do not use names as IDs; use something meaningless -- like an integer or a GUID.

There are several ways. One way to do that is with an INSERT/SELECT with a JOIN:

INSERT INTO Child ( ID )
SELECT A.ID FROM Parent A
LEFT OUTER JOIN Child B
ON A.ID=B.ID
WHERE B.ID IS NULL

Posted 23-Oct-13 10:49am

PIEBALDconsult

Solution 2

SQL

create table  student_details(roll int identity, name varchar(10));
insert into  student_details(name) values('A'), ('B');

create table  student_table(sl int identity, name varchar(10));
insert into  student_table(name) values('A'), ('B'), ('C'), ('D');

insert into student_details(name)
select name from  student_table where name not in(select name from student_details);

Posted 23-Oct-13 14:41pm

S. M. Ahasan Habib

Updated 23-Oct-13 14:47pm

v4

Solution 3

If you use sql server 2008 or letter then you can use

if oracle then

SQL

insert into student_details(name)
select name from student_table
minus
select name from student_details

if sql server then

SQL

insert into student_details(name)
select name from student_table
except
select name from student_details

Posted 23-Oct-13 14:53pm

S. M. Ahasan Habib

Updated 23-Oct-13 21:02pm

v3

Comments

Raja Sekhar S 24-Oct-13 1:09am

This one Works for Oracle.... not for Sql Server

S. M. Ahasan Habib 24-Oct-13 2:48am

thanks

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Mubshir · Accepted Answer · 2013-10-24T02:42:00

This is how i did it.

C#

foreach (DataRow row in dt.Rows)
            {
                con.Open();
                    string query = "use Sit302GroupProject " +
                        "If Not Exists(select * from Preferences where student_id =" + row["student_id"]+ ") INSERT INTO preferences (student_id) VALUES (" + row["student_id"] + ")";

                    SqlCommand cmd = new SqlCommand(query, con);

                    cmd.ExecuteNonQuery();
                    con.Close();
            }