How to denormalized data in SQL query - sql

Question

I have a table that has Clinic Names and Doctor Names. one clinic can have many doctors. I need to split this data into two tables. one with clinic info and the other with Doctor info
trying to do this in a SQL query
Table CLINIC_DOC:
ID ClinicName Doctor
------------------------
1 xyz Dr Joe
2 xyz Dr Bob
3 abc Dr Mary
4 abc Dr John
I want to split the data into the following tables like this:
Table ClinicsData:
ClinicID ClinicName
----------------------
1 xyz
2 abc
Table DoctorData:
DocId ClinicID Doctor
--------------------------
1 1 Dr Joe
2 1 Dr Bob
3 2 Dr Mary
4 2 Dr John

Answer 1

Assuming that the ID columns (ClinicID and DocID) are automatically generated and that the clinic names are unique (i.e there are no two clinics with the same name in the portion of the real world your data represents) you can try:
INSERT INTO clinicsdata
(clinicname)
SELECT DISTINCT
cd.clinicname
FROM clinic_doc cd;
INSERT INTO doctordata
(clinicid,
doctor)
SELECT c.clinicid,
cd.doctor
FROM clinic_doc cd
INNER JOIN clinicsdata c
ON c.clinicname = cd.clinicname;

Answer 2

First, you'll probably want to create the tables you're going to populate. Here's my best guess at dataypes:
CREATE TABLE ClinicsData
(
ClinicID INT IDENTITY(1,1),
ClinicName varchar(100)
)
CREATE TABLE DoctorData
(
DocID INT IDENTITY(1,1),
ClinicID INT,
Doctor VARCHAR(100)
)
Notice that I've made ClinicsData.ClinicID an IDENTITY column. This will help us to populate DoctorData later.
Next, let's populate ClinicsData with all the distinct clinic names.
INSERT INTO ClinicsData
(
ClinicName
)
SELECT DISTINCT
ClinicName
FROM CLINIC_DOC;
Now, we can utilize ClinicsData to populate DoctorData, using an INNER JOIN.
INSERT INTO DoctorData
(
ClinicID
,Doctor
)
SELECT DISTINCT
cd.ClinicID,
c_d.Doctor
FROM CLINIC_DOC c_d
INNER JOIN ClinicsData cd ON cd.ClinicName = c_d.ClinicName