[leetcode| SQL] Combine Tables

Source: Internet
Author: User
Tags mysql query

Table:Person

+-------------+---------+| Column Name | Type    |+-------------+---------+| PersonId    | int     | | FirstName   | varchar | | LastName    | varchar |+-------------+---------+personid is the primary key, column for this table.

Table:Address

+-------------+---------+| Column Name | Type    |+-------------+---------+| Addressid   | int     | | PersonId    | int     | | City        | varchar | | State       | varchar |+-------------+---------+addressid are the primary key column for this table.

Write a SQL query for a report this provides the following information for each person in the person table, regardless if There is a address for each of those people:

FirstName, LastName, city, state

Solution:

whenever we need to combine recordsfrom-or more tables, we-need to join the tables. There is common types of join and it was important to understand their differences:

    • Inner join-selects only records from both tables that has matching values. This is also the default join.
    • Outer join-does not require each record is in the same joined tables to a matching record.
      • Left Outer Join-returns All values from the left table, even if there is no match with the right table.

Since the question requires information for each person regardless if there are an address for so person, the answer is T o Use an outer join.

Either a (person left LEFT JOIN join address) or a RIGHT JOIN (address right join person).

Ans:

# Write your MySQL query statement below
SELECT Person.firstname, Person.lastname, address.city, address.state from person left JOIN Address on Person.personid=ad Dress. PersonId

[leetcode| SQL] Combine Tables

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.