select from two different tables sql code example

Example 1: how to select from two tables in sql

-- With JOIN
-- No row if id does not exist in t2
SELECT t1.name, t2.salary FROM t1 JOIN t2 on t1.id = t2.id;
SELECT t1.*, t2.salary FROM t1 JOIN t2 on t1.id = t2.id;
-- A row with a NULL salary is returned if id does not exist in t2
SELECT t1.name, t2.salary FROM t1 LEFT OUTER JOIN t2 on t1.id = t2.id;

-- With UNION: distinct values
SELECT emp_name AS name from employees
UNION
SELECT cust_name AS name from customers;

-- With UNION ALL: keeps duplicates (faster)
SELECT emp_name AS name from employees
UNION ALL
SELECT cust_name AS name from customers;

Example 2: sql join 3 tables

SELECT column-names
  FROM table-name1 JOIN table-name2 
    ON column-name1 = column-name2
 WHERE condition