Question

I want make sql query which will insert values from one table to another table by checking where condition on 1st table.

I have to check is that row present previously in 1st table or not. If not present then add otherwise don’t add.

There is query “insert into select from” pattern in sql.

I have tried following query. But it inserts many duplicates.

INSERT INTO 
    company_location (company_id, country_id, city_id)
SELECT 
    ci.company_id, hq_location, hq_city
FROM 
    company_info ci, company_location cl 
WHERE  
    ci.company_id <> cl.company_id
    AND cl.country_id <> ci.hq_location
    AND cl.city_id <> ci.hq_city;

Duplicate avoiding means that tuple (company_id, country_id, city_id) shouldn’t added again. And I have to add from more 4 tables into these table.

Also I require query for removing duplicates from company_location. i.e. combination of (company_id, country_id, city_id) should exist only single time. Keep only one tuple and remove other rows.

Answer 1

I hope this untested Script helps! It inserts every combination just once.

INSERT INTO company_location 
    (company_id,country_id,city_id)
SELECT  distinct ci.company_id, 
        ci.hq_location, 
        ci.hq_city
FROM    company_info ci  
WHERE  ci.company_id NOT IN 
        (SELECT cl1.company_id FROM company_location cl1
            WHERE cl1.country_id = ci.hq_location
            AND cl1.city_id = ci.hq_city
            AND cl1.company_id = ci.company_id)