SQL SELECT from Multiple Tables
SQL SELECT from Multiple Tables
When working with relational databases, retrieving data from multiple tables is a common requirement. The SELECT
statement allows us to fetch specific fields from different tables by using JOIN
queries to establish relationships between them.
Complete Python Course with Advance topics:-Click Here
SQL Tutorial :-Click Here
Example Query for Selecting from Multiple Tables
Let’s consider an example where we have two supplier-related tables and an orders table. Using the INNER JOIN
clause, we can retrieve relevant data from both tables:
SELECT orders.order_id, suppliers.company_name
FROM suppliers
INNER JOIN orders
ON suppliers.supplier_id = orders.supplier_id
ORDER BY order_id;
Consideration of Three Tables Example
Suppose we have three tables: two customer tables named client1
and client2
, and a sales
table that stores product sales information.
client1 Table:
client_id | first_name |
---|---|
101 | Alice |
102 | Bob |
client2 Table:
client_id | last_name |
---|---|
101 | Johnson |
102 | Smith |
sales Table:
sale_id | client_id | product_name |
---|---|---|
501 | 101 | Laptop |
502 | 102 | Smartphone |
503 | C101 | Printer |
504 | C102 | Desk |
SQL Query to Select from Multiple Tables
The following SQL query uses LEFT JOIN
to retrieve data from the sales
table while including information from both client1
and client2
tables:
SELECT s.sale_id, s.client_id, s.product_name, c1.first_name, c2.last_name
FROM sales AS s
LEFT JOIN client1 AS c1
ON s.client_id = c1.client_id
LEFT JOIN client2 AS c2
ON s.client_id = c2.client_id;
Expected Output:
sale_id | client_id | product_name | first_name | last_name |
---|---|---|---|---|
501 | 101 | Laptop | Alice | Johnson |
502 | 102 | Smartphone | Bob | Smith |
503 | C101 | Printer | NULL | NULL |
504 | C102 | Desk | NULL | NULL |
Explanation:
- The
LEFT JOIN
ensures that all records from thesales
table are returned, even if there is no matching record inclient1
orclient2
. - If a corresponding match is found in
client1
orclient2
, it retrieves the respective values; otherwise, it returnsNULL
.
Download New Real Time Projects :-Click here
Complete Advance AI topics:-Â CLICK HERE
Conclusion
Fetching data from multiple tables using SQL joins is an essential technique that helps in efficiently combining and analyzing data from different sources. With proper table relationships and join conditions, you can get meaningful insights with ease.
For more such professional tutorials, stay tuned to updategadh!
sql select multiple tables without join
sql select from multiple tables with same column name
how to select data from two tables in sql with where clause
sql select from multiple tables with conditions
sql select from multiple tables with join
select data from multiple tables in single query
sql select from multiple tables w3schools
select from multiple tables mysql
sql join
sql
sql select from multiple tables example
sql select from multiple tables oracle
sql select from multiple tables multiple columns
Post Comment