The FEEDBACK option expands a SELECT * statement into all the selected variables including any macro variables. This can be very useful to show the variable order when joining multiple tables. The results of the expanded list of columns are displayed in the SAS log. 

These options are extremely useful for understanding the choices made by the SQL optimizer - index use, which join strategy and any sorting performed. The _METHOD option returns a number of codes to the log, a few important ones are -

SQXJM – A merge join was performed

SQXJNDX  - An index join was performed.

SQXJHSJ – A Hash join was performed.

SQXSORT – A sort operation was performed.

These options can be used to debug any issues, for example detect if the correct join strategy is being used, are my indexes being used in the join?

Note: You need to specify the MSGLEVEL=I options to activate this setting.

The INOBS= option limits the number of rows that PROC SQL processes. This option can be very useful when developing a new query and testing on a limited number of records. There is also an equivalent OUTOBS= option which reduces the number of records being written by a query.

The _TREE option, provides a graphical representation of the way the query optimizer handled the execution of a query. This options shows the chosen query plan, this decision is based on multiple factors (estimated CPU and I/O). Sometime this plan may not be the most efficient. Using the TREE option can help debug.

The RESET statement is used to add, drop, or change one or more PROC SQL options without the need to restart the procedure. This example shows the FEEDBACK option being turned on and then off.

Macro variables are useful debugging tools. Two useful macros are SQLOBS and SQLRC.

The SQLOBS macro variable displays the number of rows that are processed by an SQL procedure statement.