Most, but not all, BASE SAS DATA step functions can be used in PROC SQL because these functions are part of BASE SAS, and PROC SQL is a BASE SAS procedure.

PROC SQL summary functions contain only one argument, and the column's statistic is calculated across the rows of the group.

Multiple arguments used in a PROC SQL summary function cause it to no longer be considered a summary function. In this case, PROC SQL searches BASE SAS for a like-named function. If it finds one, the statistic is calculated for the current row.

If there is no like-named BASE SAS function, an error occurs.

When you use certain DATA step functions in PROC SQL, you might encounter unexpected results, which could include the following:

• Differences in column lengths using the COALESCEC() function in PROC SQL versus the DATA step.
• Using multiple arguments in the SUM() function calculate the results for the current row.
• Using multiple arguments in the AVG() function produces the following error:
  Error: Function AVG could not be located.
  This error occurs because there is no function named AVG() in BASE SAS.
• The LAG() function cannot be used in PROC SQL.

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