In this video we see how to append data in SQL.
Appending data refers to combining result set of two or more tables into a single one. We use UNION and UNION ALL keyword in sql to append result of two or more select statement.
UNION ALL - append and return duplicate
UNION - no duplicate data will be returned
For union to happen both the tables should have same number of columns and the column name should also be same. If the column number is same and column names are different then rename the column names for union to happen.
Explained here is a simple example of appending data. There are many more applications of the same logic in different business cases.
DDL:-
--data collected by person 1
/*
create table computer_store_1(
product_id varchar(50),
product varchar(50),
brand varchar(50),
make_country varchar(50),
unit_price int,
model_year int)
*/
/*
insert into computer_store_1(product_id,product,brand,make_country,unit_price,model_year)
values('cp111','CPU','lenovo','india',1000,2020),
('mo222','Monitor','lg','korea',2000,2021),
('mo333','Monitor','sony','japan',2500,2021),
('ra444','RAM','intel','india',3000,2022),
('ra555','RAM','amd','usa',3200,2018),
('la666','Laptop','acer','usa',5500,2019),
('ma777','Macbook','apple','china',7500,2021),
('la888','Laptop','hp','india',4900,2020),
('mo999','Mouse','lenovo','korea',100,2022)
*/
--select * from computer_store_1
--data collected by 2nd person
/*
create table computer_store_2(
product_id varchar(50),
product varchar(50),
brand varchar(50),
make_country varchar(50),
unit_price int,
model_year int)
insert into computer_store_2(product_id,product,brand,make_country,unit_price,model_year)
values('cp111','CPU','lenovo','india',1000,2020),
('mo222','Monitor','lg','korea',2000,2021),
('mo333','Monitor','sony','japan',2500,2021),
('la112','laptop','samsung','korea',3000,2022),
('ta113','tablet','samsung','india',3000,2021),
('la114','laptop','dell','usa',4000,2022),
('de115','desktop','dell','usa',3700,2022)
*/
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