Select rows conditionally and insert into another table conditionally - tsql

Question

How to insert into table 2 all field values of a row from table A, where all values in a column A in table 1 that satisfy a condition on column B of table 1 ,but do not exist in table 2.How to frame a query using not exists?
I tried this:
INSERT INTO Teachermast (
teacher_code,
teacher_name,
designation,
dept_code,
contact_no,
email,
address,
dob,
PASSWORD
)
SELECT
userId,
username,
designation,
dept,
contact_no,
email,
address,
dob,
PASSWORD
FROM
UserMast
WHERE NOT EXISTS
(SELECT
userId
FROM
UserMast
WHERE usertype = '3')
but this doesnt seem to work.
Kindly help.

Answer 1

You could do a MERGE
create table users
(
userId varchar(50),
username varchar(50),
usertype int,
password varchar(50),
contact_no varchar(50),
email varchar(50),
faxno varchar(50),
address varchar(50),
created_date date,
updated_date date,
status varchar(50),
gender varchar(50),
dob date,
lasttimelogin datetime,
login_time datetime,
logoutt_time datetime,
designation varchar(50),
dept varchar(50),
email_pass varchar(50)
)
insert into users values('T0003','Ankita',3,'12345','9858‌​585245','anki#gmail.com','201','l block noid sec 25',NULL,NULL,NULL,'Female','11/09/1990',NULL,NULL,NULL,'Teacher','EC',NULL);
insert into users values('T0004','Ribha',3,'12345','9512365423','sharma#gmail.com',NULL,'221 dwarka sec 10',NULL,NULL,NULL,'Female','12/02/1989',NULL,NULL,NULL,'Teacher','EC',NULL);
create table teachers
(
teacher_code varchar(50),
teacher_name varchar(50),
designation varchar(50),
dept_code varchar(50),
contact_no varchar(50),
email varchar(50),
address varchar(50),
dob date,
password varchar(50)
)
insert into teachers values('T0002','Tanvi','Teacher','CS','9632569856','tan123#gmai‌​l.com','298 mayur vihar ph 1','29/06/1990','12345');
insert into teachers values('T0003','Ankita','Teacher','EC','9858585245','anki#gmail‌​.com','201 l block noida sec 25','11/09/1990','12345');
merge teachers as target
using (select userid, username, designation, dept, contact_no, email, address, dob, password from users where usertype = 3)
as source(userid, username, designation, dept, contact_no, email, address, dob, password)
on target.teacher_code = source.userid
when not matched by target then
insert (teacher_code, teacher_name, designation, dept_code, contact_no, email, address, dob, password)
values (source.userid, source.username, source.designation, source.dept, source.contact_no, source.email, source.address, source.dob, source.password);
select * from teachers
However, I think there are issues with your database design. With your current model, you could have, for example, a different address (or password!) for Ankita in table1 compared to table2. And if you change any of that information you would have to change it in both places.
Could you, for example, just insert everyone into "users" and have "teachers" be a view
select {columns} from users where usertype = 3

Answer 2

Please try this query
SELECT
t.userId,
t.username,
t.designation,
t.dept,
t.contact_no,
t.email,
t.address,
t.dob,
t.PASSWORD
FROM Teachermast as t
LEFT join UserMast as u on t.userId = u.teacher_code
WHERE t.usertype = '3' and u.teacher_code is null