PRB: Using "!=" in a Join Statement Does Not Return Records

MORE INFORMATION

ON Clause with !=

The following syntax does not return all the records from one table that do not have a matching record in the other table: This creates a Cartesian product that excludes records that do match.

Where Clause with !=

To create a result set that includes all records from one table that do not exist in a second table, use the following syntax: In conclusion, the following statements are not equivalent:

   SELECT * FROM tbl1 inner join tbl2 on tbl1.fld1 != tbl2.fld1
   SELECT * FROM tbl1 WHERE tbl1.fld1 != tbl2.fld1
				

Steps to Reproduce Behavior

Place the following code in a program file and run the code. Note that there are no records returned in the cursor.

   CREATE DATABASE MyTest
   CREATE TABLE tbl1 (fld1 c(10),fld2 c(20))
   CREATE TABLE tbl2 (fld1 c(10), fld2 c(20))
   INSERT INTO tbl1 VALUES('1','Rec1')
   INSERT INTO tbl1 VALUES ('2','Rec2')
   SELECT * INTO CURSOR MyCurse FROM tbl1 inner JOIN tbl2 ON ;
   tbl1.fld1 != tbl2.fld1
				

For a demonstration of the Cartesian product, run the following code with the database created in the code above open:

   INSERT INTO tbl2 VALUES ('1','tbl2Rec1')
   INSERT INTO tbl2 VALUES ('2','tbl2Rec2')
   SELECT * INTO CURSOR MyCurse FROM tbl1 inner JOIN tbl2 ON ;
   tbl1.fld1 != tbl2.fld1