Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations bkrike on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
-
To join n tables together, you need a minimum of (n-1) join conditions
In Oracle, An Introduction to SQL and PL/SQL, there is a discussion of Joins. The statement follows: To join n tables together, you need a minimum of (n-1) join conditions. The use of the words "At Least" Indicates I can do the following: where table1.column1 = table2.column2... -
invalid joins
In An Introduction to SQL and PL/SQL, Oracle, lesson 4 there is a discussion of Cartesian products. The following statement is in the slides. Cartesian Product A Cartesian product is generated if a join condition is omitted OR a join condition is invalid. What is an example of an invalid join? -
null value in subqueries
Please help me understand the following from Oracle Introduction to SQL and PL/SQL, Lesson 7 subqueries. select ename from emp where empno NOT IN (select mgr from emp); no rows returned. Returning Nulls in the Resulting Set of a Subquery The SQL statement above attempts...
