Ever wanted to be able to see records before committing them? I bet you have. It is not possible in Dynamics AX, but you can do it in SQL Server Management Studio. It is really easy as well.
Start Management Studio and connect to the SQL Server. Now navigate to Tools -> Options. From there, Query Execution -> SQL Server -> Advanced. There is a setting called SET TRANSACTION ISOLATION LEVEL. Set it to READ UNCOMMITED. Click OK button and you are done.
Just remember that unless you always want to see uncommited data, it is good to reset this setting once done.
Want to Update, Insert and Delete when comparing one table against another in just one go. Merge is what you are looking for. It is explained in steps here: http://www.made2mentor.com/2013/05/writing-t-sql-merge-statements-the-right-way/
Find it hard to know what type of join to use when writing code in SQL? This is the best page I have seen explaining it: https://www.codeproject.com/kb/database/visual_sql_joins.aspx