They are not the same thing. Consider these queries: SELECT * FROM Orders LEFT JOIN OrderLines ON OrderLines.OrderID=Orders.ID WHERE Orders.ID = 12345 and SELECT * FROM Orders LEFT JOIN OrderLines ON OrderLines.OrderID=Orders.ID AND Orders.ID = 12345 The first will return an order and its lines, if any, for order number 12345. The second will return … Read more
You don’t quite have SQL Server’s proprietary UPDATE FROM syntax down. Also not sure why you needed to join on the CommonField and also filter on it afterward. Try this: UPDATE t1 SET t1.CalculatedColumn = t2.[Calculated Column] FROM dbo.Table1 AS t1 INNER JOIN dbo.Table2 AS t2 ON t1.CommonField = t2.[Common Field] WHERE t1.BatchNo = ‘110’; … Read more
Sub-queries are the logically correct way to solve problems of the form, “Get facts from A, conditional on facts from B”. In such instances, it makes more logical sense to stick B in a sub-query than to do a join. It is also safer, in a practical sense, since you don’t have to be cautious … Read more
INNER JOIN is ANSI syntax that you should use. It is generally considered more readable, especially when you join lots of tables. It can also be easily replaced with an OUTER JOIN whenever a need arises. The WHERE syntax is more relational model oriented. A result of two tables JOINed is a cartesian product of … Read more
I believe an UPDATE FROM with a JOIN will help: MS SQL UPDATE Sales_Import SET Sales_Import.AccountNumber = RAN.AccountNumber FROM Sales_Import SI INNER JOIN RetrieveAccountNumber RAN ON SI.LeadID = RAN.LeadID; MySQL and MariaDB UPDATE Sales_Import SI, RetrieveAccountNumber RAN SET SI.AccountNumber = RAN.AccountNumber WHERE SI.LeadID = RAN.LeadID;
They are functionally equivalent, but INNER JOIN can be a bit clearer to read, especially if the query has other join types (i.e. LEFT or RIGHT or CROSS) included in it.
Reading this original article on The Code Project will help you a lot: Visual Representation of SQL Joins. Also check this post: SQL SERVER – Better Performance – LEFT JOIN or NOT IN?. Find original one at: Difference between JOIN and OUTER JOIN in MySQL.