@mrzlatan91 wrote: Hi guys, unfortunately I have a problem using Macrovariables. My datasets look like this:   Note, that every index of Table a represents a corresponding value column of table b. That means, that e.g. the values of ID 124 (Index 1) are represented in the column of table b. Now, in my macro, I do some checks and want to set some specific value columns to missing. To try this, I used the following code: How is 124 "represented" in which column of table b?   When you get an error copy the code submitted and the error messages from the log and paste into a code box opened using the forum {I} menu icon to preserve formatting of the error messages.     Show what your desired output would look like for your examples. And explain your rules a little. You show a macro variable, &lostid,  but not it's value. So we don't know what you might actually be looking for. Is &lostid ever likely to be duplicated in different records of work.a? If so your sql will always select the first index where it appears as written.     Your example work.a would have ID value of 3535 for index 4. Is that actually what you intended?   ... View more

Alex: Learning to link data tables via hash indexes offers you a chance to learn more about how database systems optimize inner joins. I suspect that your professor knows that in SAS SQL an ordinary inner join of two tables, if a hash index of one will fit into memory, will optimize as a scan of a dynamic hash index. Even so, once you learn how to program the inner join using a hash index, it will be easier to learn how to program a left join using a hash index. The SAS SQL compiler does not, last time I checked, optimize a left join. So except for academic purposes, a SAS SQL SELECT ... FROM r1 INNER JOIN r2 ON r1.key = r2.key will usually execute as fast or faster than a Data step that generates a hash index. Over on the SAS-L side, that discussion has continued off and on for decades. S ... View more