sasjs/skills

SAS Language

Write idiomatic, production-quality SAS code. This skill covers the SAS language itself, independent of any framework.

Scope

• DATA step programming (SET/MERGE/BY, RETAIN, arrays, DO loops, hash objects, first./last. processing)
• PROC SQL (joins, subqueries, views, pass-through with CONNECT TO)
• Macro language (%macro/%mend, macro variables, %local/%global, conditional %IF logic, quoting functions %STR/%NRSTR/%BQUOTE, CALL SYMPUTX)
• Common PROCs: SORT, MEANS/SUMMARY, FREQ, TRANSPOSE, REPORT, PRINT, CONTENTS, DATASETS, FORMAT, IMPORT/EXPORT
• Formats and informats (user-defined via PROC FORMAT, picture formats)
• ODS output (HTML, PDF, RTF, Excel, OUTPUT destination)
• File I/O: LIBNAME, FILENAME, INFILE/INPUT, FILE/PUT

Workflow

Apply this loop to every request that produces SAS code — new program, edit, or debug:

1. Analyze the request. Identify the input(s): datasets, columns, macro variables, platform (SAS 9 vs Viya). Note the desired output: a dataset, a report (ODS), a macro variable, a file. If the request is ambiguous, state your assumption and proceed.
2. Draft the code. Write the minimum correct program following the Style rules below. Use 2-level dataset names, explicit length for character variables, %local inside macros, and quit; for proc sql. Prefer proc sort nodupkey over hand-rolled dedup.
3. Run it (or describe the run). If a SAS session is available, submit and capture the log. If not, trace the code mentally against the Common pitfalls list — call out any step you could not verify.
4. Inspect the log. Treat any WARNING: or ERROR: as a defect to fix, not a note to ignore. Common culprits: uninitialized variables, implicit numeric→character conversion, truncation from implicit length=8, "no observations", unresolved macro references, read-only automatic macro variables. Superfluous NOTEs should also be trimmed where reasonable.
5. Review against pitfalls. Re-read the final code against the Common pitfalls list before returning it. Fix or annotate anything flagged.

Inputs: a request (natural language or a .sas file), optionally sample data or a log excerpt. Outputs: idiomatic SAS code (2-space indented, run;/quit; terminated) plus, when useful, a short note on any pitfall addressed or assumption made. Verification: the returned code passes a mental log-scan with zero WARNING/ERROR, and a real run (when available) produces a clean log.

Non-negotiable: no WARNINGs

Generated SAS code must run cleanly — zero WARNINGs (and zero ERRORs) in the log. Treat every WARNING: as a defect: uninitialized variables, implicit type conversions, truncation notes that should be warnings, "no observations", unresolved macro references, etc. If a warning is truly unavoidable, suppress it deliberately (e.g. an explicit option) and comment why. Likewise avoid superfluous NOTEs where reasonable.

Style rules

These follow the @sasjs/core coding standards — apply them to all SAS code:

• One statement per line; indentation = 2 spaces, no tabs, no trailing whitespace
• Lines no longer than 80 characters; unix (LF) line endings; UTF-8
• Avoid non-ASCII / special characters entirely — maximum compatibility across SAS installations and encodings
• Always end steps with run;; for proc sql (and CAS-connected procs) quit; is essential to avoid WARNING: You cannot disconnect or terminate session ... on Viya
• All dataset references must be 2-level (work.blah, not blah) — protects against DATASTMTCHK=ALLKEYWORDS and an active USER library
• Explicit length / attrib for character variables rather than relying on defaults (avoids implicit length=8 truncation)
• Use literal suffixes for clarity ('01JAN2020'd, '12:30't)
• Prefer proc sort with nodupkey over manual dedup logic
• Macros:
  • Define with parentheses, even with no parameters: %macro x(); not %macro x;
  • Closing %mend; must repeat the macro name
  • Macro calls are not terminated with a semicolon: %my_macro() not %my_macro();
  • Mandatory parameters positional; optional parameters keyword (var=) style
  • Macro names lowercase, verb-noun convention
  • Macro variables without trailing dot (&var not &var.) unless needed to prevent incorrect resolution
  • Macro variable NAMES are case-insensitive: &Foo, &FOO, and &foo all resolve to the same symbol (same for %symexist/%superq/symget arguments, which take a NAME not a value). Don't chase case mismatches as a bug — it's never the cause.
  • ALL macro variables must be %local unless deliberately global (globals should use an application prefix to avoid collisions); use call symputx (not symput) in DATA steps
  • Comment with /* */ inside macros (asterisk comments are compiled into the macro)
  • Guard macro logic with %length(&var)=0 checks rather than &var= (empty comparisons are unsafe)
• Avoid naming collisions: use %sysfunc-/&syslast-based work tables (e.g. data &output; set &syslast; run;) rather than hard-coded names
• WORK library is auto-cleared on session termination: SAS deletes every table in WORK when the session ends, so explicit cleanup (proc datasets lib=work nolist; delete ...; quit;) is not required for ordinary temporary tables — do not add it, and do not flag its absence as a defect in review. Clean up explicitly only when temp files are large or voluminous enough to risk disk pressure mid-run; in that case, drop them as soon as they are no longer needed rather than leaving them for end-of-session disposal.
• No open (non-macro) conditional code: wrap platform-branching or conditionally-executed blocks (e.g. %if %mf_getplatform()=VIYA %then %do; ... %end;) in a %macro ... %mend and invoke the macro. Open %if at program level fails in some execution contexts (job/scheduler/test harnesses) and hides scope leaks.

Portability awareness

• Note when code differs between SAS 9.4 and Viya (e.g. CAS actions vs procs, proc casutil for sashdat loading, no X command on locked-down servers)
• Avoid hard-coded physical paths and engine-specific options unless asked
• No open macro code with if/else logic: wrap branching blocks in %macro ... %mend and call them — open %if/%else does not behave as expected in all SAS environments.

Before / after examples

Each pair shows a common WARNING- or defect-prone pattern and the idiomatic fix, with the log issue it addresses.

DATA step: uninitialized variable + implicit length truncation

Before — region is referenced but never assigned or brought in via set, so the log shows WARNING: Variable region is uninitialized; and name inherits the length of first_name from the source (often $8), silently truncating the concatenated value:

data work.customers;
  set work.source;
  region = upcase(region);                 /* region not in work.source */
  name = catx(' ', first_name, last_name); /* truncated to source length of name */
run;

After — region is brought in via set (or explicitly assigned), and an explicit length before set widens name so catx is not truncated:

data work.customers;
  length name $ 50;
  set work.source;                          /* region must exist in work.source */
  region = upcase(region);
  name = catx(' ', first_name, last_name);
run;

PROC SQL: implicit conversion + cartesian product

Before — joining on character id vs numeric cust_id triggers NOTE: Character values have been converted to numeric (or a WARNING under some options), and the missing join key risks a cartesian blow-up:

proc sql;
  create table work.joined as
  select a.*, b.balance
  from work.orders a, work.accounts b
  where a.id = b.cust_id;
quit;

After — explicit length/cast so types match, explicit inner join, and a guard against the cartesian if keys are missing:

proc sql;
  create table work.joined as
  select a.id, a.amount, b.balance
  from work.orders as a
  inner join work.accounts as b
    on a.id = input(b.cust_id, 8.) /* explicit cast; or fix upstream length */
  ;
quit;

If a key column legitimately has duplicates on both sides, aggregate or dedup first — never rely on an accidental 1:1 join.

Macro: missing %local + unsafe empty check

Before — %let inside the macro creates dsid in global scope (no %local), and %if &filter= is unsafe — when &filter is empty it resolves to %if = %then, a syntax error rather than a clean branch:

%macro apply_filter(filter=);
  %if &filter= %then %do;
    data work.out; set work.in; run;
  %end;
  %else %do;
    data work.out; set work.in; where &filter; run;
  %end;
  %let dsid = &syslast;
%mend apply_filter;

After — %local dsid keeps the temp variable in macro scope, %length(&filter)=0 guards the empty check safely, parentheses on the macro definition, and %mend repeats the name:

%macro apply_filter(filter=);
  %local dsid;
  %if %length(&filter)=0 %then %do;
    data work.out; set work.in; run;
  %end;
  %else %do;
    data work.out; set work.in; where &filter; run;
  %end;
  %let dsid = &syslast;
%mend apply_filter;

Common pitfalls to flag when reviewing

• Unintended many-to-many MERGEs
• Automatic variable _ERROR_ / implicit RETAIN surprises
• Macro timing issues: referencing &macrovar before it exists, %if evaluating data-step variables (use if/symget instead)
• Automatic macro variables (&syscc, &syswarningtext, &syserrortext, &sysdate, &sysuserid, etc.) are READ-ONLY — attempting to overwrite them (e.g. %let syswarningtext=; or call symput('syscc',...)) raises ERROR: Unable to assign value to a macro variable that is read only (or similar). Never try to "clear" them.
• Truncation from implicit length=8 on first assignment
• proc sql cartesian product warnings

Limitations

This skill is a static language reference — it provides guidance for writing and reviewing SAS code. It does not execute SAS code, run shell commands, access the filesystem, connect to databases, or make network requests. All code examples are illustrative and must be submitted to a SAS session by the user. Terms like "File I/O", "PROC SQL", "command", and "execution" refer to SAS language concepts (file-handling statements, SQL procedure, macro execution contexts), not to operating-system-level operations performed by this skill.