how to join tables in sql
JOINING 2 Tables in sql
SELECT X.Column_Name , Y.Column_Name2
FROM TABLES1_NAME X
INNER JOIN TABLES2_NAME Y ON X.Primary_key = Y.Foreign_key;
--FOR EXAMPLE
--GET THE FIRST_NAME AND JOB_TITLE
--USE EMPLOYEES AND JOBS TABLE
--THE RELATIONSHIP IS JOB_ID
SELECT E.FIRST_NAME , J.JOB_TITLE
FROM EMPLOYEES E
INNER JOIN JOBS J ON J.JOB_ID = E.JOB_ID;join three tables sql
Suppose we are having three table named as
Student_details
Attendance_details
Batch_details
And we have to apply join these three tables for fetching records
Example query:
select column_names
from Student_detail as s join Attendance_details as a on
s.s_id = a.s_id join Batch_details as b on
s.s_id = b.s_id;
Here in the above example we implemented simple join but you change it with own join requirements.self join in sql
Self is joining a table to itself.
-- assume employee table as 2 different table using different alias
-- as manager and worker
-- we want to join these 2 virtual manager and worker table
-- to get manager's first name and worker's first name
-- our condition is worker's manager_id match managers employee id
SELECT manager.FIRST_NAME AS MANAGER_NAME ,
worker.FIRST_NAME AS WORKER_NAME
FROM EMPLOYEES manager
INNER JOIN EMPLOYEES worker on worker.MANAGER_ID = manager.EMPLOYEE_ID
order by 1
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