How to compare and insert different tables in sql? - sql

Question

I have two different databases, the same column.I want to copy from the old database to the new database by comparing the student ID numbers between the tables and having the same number.
For example:
Database name 1: StudentInformation, table name: Student
StudentID Image
---------------------
123 1.png
142 2.png
175 3.png
475 4.png
Database name 2: StudentInformation2, table name: NewStudent
StudentID Image
--------------------------
145 a14.png
196 7.png
175 Null
875 9.png
475 Null
The two tables have common IDs (ID=175 and ID=475)
I want to get this table as a result:
New StudentInformation3, table name: NewSameStudents
StudentID Image
----------------------
175 3.png
475 4.png

Answer 1

You should try using the Merge Statement of SQL Server
Merge Statement Here

Answer 2

Here is one approach:
SELECT s1.StudentID, s1.Image
FROM StudentInformation.[schema].student s1
WHERE EXISTS (SELECT 1
FROM StudentInformation2.[schema].NewStudent s2
WHERE s1.StudentID = s2.StudentID
);
Demo
If you want to populate a new table using the results from the above select, then you may use the INSERT INTO ... SELECT construct:
INSERT INTO StudentInformation3.[schema].NewSameStudents (StudentID, Image)
SELECT s1.StudentID, s1.Image
FROM StudentInformation.[schema].student s1
WHERE EXISTS (SELECT 1
FROM StudentInformation2.[schema].NewStudent s2
WHERE s1.StudentID = s2.StudentID
);
But, I might recommend against this, since you can just create a (non materialized) view using the first query. Also, NewSameStudents is a derived table, and therefore might have to updated frequently, which could be a hassle.

Answer 3

Use inner join and isert into select statement for inserting in new table
insert into NewSameStudents(studentid,image)
select a.studentid,a.image from Student a inner join newstudent n
on a.studentid=n.studentid
where n.image is null

Answer 4

Below is the fully qualified SQL Query where it allows to select data between databases and even between different database servers.
SELECT * FROM [SERVER].[DATABASE].[SCHEMA].[TABLE]
SELECT
a.StudentID,
b.Image
FROM
StudentInformation.Student a
JOIN
StudentInformation2.Student b
ON a.StudentID = b.StudentID

Answer 5

Your 3rd table make no sense if you mean
New StudentInformation3, table name: NewSameStudents
StudentID Image
----------------------
175 3.png
475 4.png
You can use inner join
SELECT StudentID,Image
FROM StudentInformation1
INNER JOIN StudentInformation2
ON StudentInformation1.StudentID = StudentInformation1.StudentID;

Answer 6

try this:
WITH StudentInformation AS (
SELECT 123 AS StudentID, '1.png' AS Image UNION ALL
SELECT 142, '2.png' UNION ALL
SELECT 175, '3.png' UNION ALL
SELECT 475, '4.png'
),
StudentInformation2 AS (
SELECT 145 AS StudentID, 'a14.png' AS Image UNION ALL
SELECT 196, '7.png' UNION ALL
SELECT 175, NULL UNION ALL
SELECT 875, '9.png' UNION ALL
SELECT 475, NULL
)
SELECT s1.StudentID, s1.Image
FROM StudentInformation2 s2 left join
StudentInformation s1 ON s1.StudentID = S2.StudentID

Answer 7

Use Merge From SQL:
Merge into [TABLE_TARGET] as u
USING (Select * from TABLE) as c
on
u.FIELD1 = c.FIELD2 ---JOIN
--------------------
WHEN MATCHED THEN
-------------------
Update SET
FIELD_FROM_TARGET = c.FIELD_FROM_TABLE
----------------------
WHEN NOT MATCHED THEN
----------------------
Insert (
FIELD_FROM_TARGET
) VALUES
(
FIELD_FROM_TABLE
);