Top 50 Sas Programming Interview Questions You Must Prepare 24.Jun.2024

Q1. How Are Numeric And Character Missing Values Represented Internally?

Character as Blank or  and Numeric as.

Q2. How Would You Create Multiple Observations From A Single Observation?

Using double Trailing @@.

Q3. What Is The Use Of Proc Sql?

PROC SQL is a powerful tool in SAS, which combines the functionality of data and proc steps. PROC SQL can sort, summarize, subset, join (merge), and concatenate datasets, create new variables, and print the results or create a new dataset all in one step! PROC SQL uses fewer resources when compared to that of data and proc steps. To join files in PROC SQL it does not require to sort the data prior to merging, which is must, is data merge.

Q4. What Techniques And/or Procs Do You Use For Tables?

Proc Freq, Proc univariate, Proc Tabulate & Proc Report.

Q5. What Is The Difference Between: X=a+b+c+d; And X=sum (of A, B, C ,d);?

Is anyone wondering why you wouldn’t just use total=field1+field2+field3;

Q6. What Are Some Good Sas Programming Practices For Processing Very Large Data Sets?

Sampling method using OBS option or subsetting, commenting the Lines, Use Data Null.

Q7. What Is The Different Between Functions And Procs That Calculate The Same Simple Descriptive Statistics?

Proc can be used with wider scope and the results can be sent to a different dataset. Functions usually affect the existing datasets.

Q8. How Would You Create A Data Set With 1 Observation And 30 Variables From A Data Set With 30 Observations And 1 Variable?

Using PROC TRANSPOSE.

Q9. What Versions Of Sas Have You Used (on Which Platforms)?

SAS 9.1.3,9.0, 8.2 in Windows and UNIX, SAS 7 and 6.12.

Q10. How Do The In= Variables Improve The Capability Of A Merge?

The IN=variablesWhat if you want to keep in the output data set of a merge only the matches (only those observations to which both input data sets contribute)? SAS will set up for you special temporary variables, called the "IN=" variables, so that you can do this and more. Here's what you have to do: signal to SAS on the MERGE statement that you need the IN= variables for the input data set(s) use the IN= variables in the data step appropriately, So to keep only the matches in the match-merge above, ask for the IN= variables and use them:data three;merge one(in=x) two(in=y); /* x & y are your choices of names */by id; /* for the IN= variables for data */if x=1 and y=1; /* sets one and two respectively */run;

Q11. How Does Sas Handle Missing Values In: Assignment Statements, Functions, A Merge, An Update, Sort Order, Formats, Procs?

Missing values will be assigned as missing in Assignment statement. Sort order treats missing as second smallest followed by underscore.

Q12. For What Purpose Would You Use The Retain Statement?

The retain statement is used to hold the values of variables across iterations of the data step. Normally, all variables in the data step are set to missing at the start of each iteration of the data step. What is the order of evaluation of the comparison operators: + - * / ** ()?A) (), **, *, /, +, -.

Q13. How Do You Debug And Test Your Sas Programs?

First thing is look into Log for errors or warning or NOTE in some cases or use the debugger in SAS data step.

Q14. What Do The Mod And Int Function Do? What Do The Pad And Dim Functions Do?

MOD: Modulo is a constant or numeric variable, the function returns the reminder after numeric value divided by modulo.

INT: It returns the integer portion of a numeric value truncating the decimal portion.

PAD: it pads each record with blanks so that all data lines have the same length. It is used in the INFILE statement. It is useful only when missing data occurs at the end of the record.

CATX: concatenate character strings, removes leading and trailing blanks and inserts separators.

SCAN: it returns a specified word from a character value. Scan function assigns a length of 200 to each target variable.

SUBSTR: extracts a sub string and replaces character values.Extraction of a substring:
Middleinitial=substr(middlename,1,1); Replacing character values: substr (phone,1,3)=’433’; If SUBSTR function is on the left side of a statement, the function replaces the contents of the character variable.

TRIM: trims the trailing blanks from the character values.

SCAN vs. SUBSTR: SCAN extracts words within a value that is marked by delimiters. SUBSTR extracts a portion of the value by stating the specific location. It is best used when we know the exact position of the sub string to extract from a character value.

Q15. Why Is Sas Considered Self-documenting?

SAS is considered self documenting because during the compilation time it creates and stores all the information about the data set like the time and date of the data set creation later No. of the variables later labels all that kind of info inside the dataset and you can look at that info using proc contents procedure.

Q16. How Could You Generate Test Data With No Input Data?

Using Data Null and put statement.

Q17. What Is The Purpose Of _error_?

It has only to values, which are 1 for error and 0 for no error.

Q18. What Do The Sas Log Messages "numeric Values Have Been Converted To Character" Mean? What Are The Implications?

It implies that automatic conversion took place to make character functions possible.

Q19. What Has Been Your Most Common Programming Mistake?

Missing semicolon and not checking log after submitting program, Not using debugging techniques and not using Fsview option vigorously.

Q20. Why Is A Stop Statement Needed For The Point=option On A Set Statement?

When you use the POINT= option, you must include a STOP statement to stop DATA step processing, programming logic that checks for an invalid value of the POINT= variable, or Both. Because POINT= reads only those observations that are specified in the DO statement, SAS cannot read an end-of-file indicator as it would if the file were being read sequentially. Because reading an end-of-file indicator ends a DATA step automatically, failure to substitute another means of ending the DATA step when you use POINT= can cause the DATA step to go into a continuous loop.

Q21. What Other Sas Products Have You Used And Consider Yourself Proficient In Using?

Data _NULL_ statement, Proc Means, Proc Report, Proc tabulate, Proc freq and Proc print, Proc Univariate etc.

Q22. What Is The Difference Between Nodup And Nodupkey Options?

NODUP compares all the variables in our dataset while NODUPKEY compares just the BY variables.

Q23. What Is A Method For Assigning First.var And Last.var To The By Groupvariable On Unsorted Data?

In unsorted data you can't use First. or Last.

Q24. Do You Prefer Proc Report Or Proc Tabulate? Why?

I prefer to use Proc report until I have to create cross tabulation tables, because, It gives me so many options to modify the look up of my table, (ex: Width option, by this we can change the width of each column in the table) Where as Proc tabulate unable to produce some of the things in my table. Ex: tabulate doesn’t produce n (%) in the desirable format.

Q25. What Is Enterprise Guide? What Is The Use Of It?

It is an approach to import text files with SAS (It comes free with Base SAS version 9.0).

Q26. How Can You Import .csv File In To Sas?

To create CSV file, we have to open notepad, then, declare the variables.

  proc import datafile='E:age.csv' 
out=sarath dbms=csv replace;
getnames=yes;
run;

Q27. How Do You Test For Missing Values?

Using Subset functions like IF then Else, Where and Select.

Q28. How Would You Determine The Number Of Missing Or Nonmissing Values In Computations?

To determine the number of missing values that are excluded in a computation, use the NMISS function.

data _null_;
m = . ;
y = 4 ;
z = 0 ;
N = N(m , y, z);
NMISS = NMISS (m , y, z);
run;

The above program results in N = 2 (Number of non missing values) and NMISS = 1 (number of missing values).

Q29. What Are Sas/access And Sas/connect?

SAS/Access only process through the databases like Oracle, SQL-server, Ms-Access etc.
SAS/Connect only use Server connection.

Q30. What Does The Run Statement Do?

When SAS editor looks at Run it starts compiling the data or proc step, if you have more than one data step or proc step or if you have a proc step. Following the data step then you can avoid the usage of the run statement.

Q31. How Can You Create Zero Observation Dataset?

Creating a data set by using the like clause.ex: proc sql;create table latha.emp like oracle.emp;quit;In this the like clause triggers the existing table structure to be copied to the new table. using this method result in the creation of an empty table.
In the editor window we write%include 'path of the sas file';run;if it is with non-windowing environment no need to give run statement.

Q32. How Can You Put A "trace" In Your Program?

By using ODS TRACE ON.

Q33. What Is The One Statement To Set The Criteria Of Data That Can Be Coded In Any Step?

Options statement.

Q34. What Are The New Features Included In The New Version Of Sas I.e., Sas9.1.3?

The main advantage of version 9 is faster execution of applications and centralized access of data and support.

There are lots of changes has been made in the version 9 when we compared with the version @The following are the few:

  • SAS version 9 supports Formats longer than 8 bytes & is not possible with version @
  • Length for Numeric format allowed in version 9 is 32 where as 8 in version @
  • Length for Character names in version 9 is 31 where as in version 8 is 3@
  • Length for numeric informat in version 9 is 31, 8 in version @

Length for character names is 30, 32 in version 8.3 new informats are available in version 9 to convert various date, time and datetime forms of data into a SAS date or SAS time.

  • ANYDTDTEW. - Converts to a SAS date value
  • ANYDTTMEW. - Converts to a SAS time value.
  • ANYDTDTMW. -Converts to a SAS datetime value.CALL SYMPUTX Macro statement is added in the version 9 which creates a macro variable at execution time in the data step by
  • Trimming trailing blanks
  • Automatically converting numeric value to character.

New ODS option (COLUMN OPTION) is included to create a multiple columns in the output.

Q35. What Is The Difference Between Calculating The 'mean' Using The Mean Function And Proc Means?

By default Proc Means calculate the summary statistics like N, Mean, Std deviation, Minimum and maximum, Where as Mean function compute only the mean values.

Q36. What Are _numeric_ And _character_ And What Do They Do?

Will either read or writes all numeric and character variables in dataset.

Q37. Name Several Ways To Achieve Efficiency In Your Program?

Efficiency and performance strategies can be classified into 5 different areas.
•CPU time
•Data Storage
• Elapsed time
• Input/Output
• Memory CPU Time and Elapsed Time- Base line measurements.

Q38. What Can You Learn From The Sas Log When Debugging?

It will display the execution of whole program and the logic. It will also display the error with line number so that you can and edit the program.

Q39. What Are Input Dataset And Output Dataset Options?

Input data set options are obs, firstobs, where, in output data set options compress, reuse.Both input and output dataset options include keep, drop, rename, obs, first obs.

Q40. First, How Do You Want Missing Values Handled?

The SUM function returns the sum of non-missing values. If you choose addition, you will get a missing value for the result if any of the fields are missing. Which one is appropriate depends upon your needs.However, there is an advantage to use the SUM function even if you want the results to be missing. If you have more than a couple fields, you can often use shortcuts in writing the field names If your fields are not numbered sequentially but are stored in the program data vector together then you can use: total=SUM(of fielda--zfield); Just make sure you remember the “of” and the double dashes or your code will run but you won’t get your intended results. Mean is another function where the function will calculate differently than the writing out the formula if you have missing values.There is a field containing a date. It needs to be displayed in the format "ddmonyy" if it's before 1975, "dd mon ccyy" if it's after 1985, and as 'Disco Years' if it's between 1975 and 1985.

Q41. What Are Some Problems You Might Encounter In Processing Missing Values? In Data Steps? Arithmetic? Comparisons? Functions? Classifying Data?

The result of any operation with missing value will result in missing value. Most SAS statistical procedures exclude observations with any missing variable values from an analysis.

Q42. If You Were Told To Create Many Records From One Record, Show How You Would Do This Using Array And With Proc Transpose?

Declare array for number of variables in the record and then used Do loop Proc Transpose with VAR statement.

Q43. Which Date Functions Advances A Date Time Or Date/time Value By A Given Interval?

INTNX.

Q44. What Is The Effect Of The Options Statement Errors=1?

The –ERROR- variable has a value of 1 if there is an error in the data for that observation and 0 if it is not.

Q45. Which Date Function Advances A Date, Time Or Datetime Value By A Given Interval?

INTNX: INTNX function advances a date, time, or datetime value by a given interval, and returns a date, time, or datetime value.
Ex: INTNX(interval,start-from,number-of-increments,alignment)

INTCK: INTCK(interval,start-of-period,end-of-period) is an interval functioncounts the number of intervals between two give SAS dates, Time and/or datetime.

DATETIME () returns the current date and time of day.

DATDIF (sdate,edate,basis): returns the number of days between two dates.

Q46. In The Flow Of Data Step Processing, What Is The First Action In A Typical Data Step?

When you submit a DATA step, SAS processes the DATA step and then creates a new SAS data set.( creation of input buffer and PDV)
Compilation Phase
Execution Phase.

Q47. What Is The Significance Of The 'of' In X=sum (of A1-a4, A6, A9);

If don’t use the OF function it might not be interpreted as we expect. For example the function above calculates the sum of a1 minus a4 plus a6 and a9 and not the whole sum of a1 to a4 & a6 and a@It is true for mean option also.

Q48. What Are The Scrubbing Procedures In Sas?

Proc Sort with nodupkey option, because it will eliminate the duplicate values.

Q49. Do You Need To Know If There Are Any Missing Values?

Just use: missing_values=MISSING(field1,field2,field3);
This function simply returns 0 if there aren't any or 1 if there are missing values.If you need to know how many missing values you have then use num_missing=NMISS(field1,field2,field3);
You can also find the number of non-missing values with non_missing=N (field1,field2,field3);

Q50. What Are Some Differences Between Proc Summary And Proc Means?

Proc means by default give you the output in the output window and you can stop this by the option NOPRINT and can take the output in the separate file by the statement OUTPUTOUT= , But, proc summary doesn't give the default output, we have to explicitly give the output statement and then print the data by giving PRINT option to see the result.