SQL Inner Join Examples

SQL Inner Join query with (=) operator:
 
SELECT C.CATEGORYID, C.CATEGORYNAME, P.PRODUCTID, P.PRODUCTNAME, P.UNITPRICE
FROM CATEGORIES C INNER JOIN
PRODUCTS P ON P.CATEGORYID = C.CATEGORYID
WHERE P.UNITPRICE = 10
ORDER BY C.CATEGORYNAME, P.PRODUCTNAME
 
This inner join query will return the categoryid, categoryname, productid, productname, unitprice where product unit price = 10
 
SQL Inner Join Query with (>) operator:
 
SELECT DISTINCT C.CATEGORYID, C.CATEGORYNAME
FROM CATEGORIES C INNER JOIN
PRODUCTS P ON C.CATEGORYID > P.CATEGORYID
WHERE P.UNITPRICE = 10
ORDER BY C.CATEGORYNAME
 
This inner join query will return the categoryId, categoryName having products with unit price=10
 

SQL Inner Join Query with not equal (<>) operator:
 
SELECT DISTINCT P1.PRODUCTNAME, P1.UNITPRICE, P1.SUPPLIERID
FROM PRODUCTS P1 INNER JOIN PRODUCTS P2
ON
P1.SUPPLIERID=P2.SUPPLIERID
AND P1.UNITPRICE<>P2.UNITPRICE
WHERE P1.UNITPRICE < 20 AND P2.UNITPRICE < 20
ORDER BY P1.SUPPLIERID
 
Inner Join with not equal operator is rarely used in self joins. As an example above sql self join query returns the productname, unitprice, supplierid where suppliers having 2 or more than 2 products with unit price less than 20.