Frequently asked SAS Interview Questions and Answers:
In this article, we will take a look at some of the basic as well as advanced concepts of SAS programming through most frequently asked SAS interview question and answers.
Statistical Analysis System, commonly known as SAS is considered as a set of multiple software that is integrated and used for various operations like Data Management, Predictive – Perspective & Descriptive Analysis, Quality Improvement, Business Analysis, Application Development, etc.
SAS’s large number of components customization, as well as extensive programming approach feature together, performs Data Analysis and Data transformation tasks. It can run on any operating system (Linux, Windows, etc) as it is platform independent.
Most Popular SAS Interview Questions and Answers
Here we go..
Q #1) Enlist the functions performed by SAS.
Answer: Well SAS (Statistical Analysis System) has its own importance in every business domain.
Enlisted below are some of the summarized functions that are performed by SAS:
- Data Management and Project Management
- Data Warehousing
- Operational Research and decisional support
- Information Retrieval and Quality Management
- Business Planning
- Statistical Analysis
Q #2) What are the 3 components in SAS programming?
Answer: The 3 components in SAS programming are:
Q #3) Enlist the syntax rules followed in SAS statements.
Answer: SAS program is written in Editor Window. Here it contains a series of statements followed by proper syntax in an order for the SAS program to understand it.
Some of the syntax rules that are followed in case of Statement component of SAS are as follows:
- End of any statement is marked by a semicolon (;).
- A semicolon is also used to separate multiple statements that appear on a single line.
- SAS statements are not case sensitive and extra spacing before statements are automatically removed.
- Comments can be included in SAS program for statements in two different ways as:
- A line beginning with an asterisk (*) and ending with a semicolon (;).
- A line beginning with a forwarding slash and an asterisk (/*) and ending with an asterisk and a forward slash (*/).
Q #4) What are the data types that SAS contain?
Answer: ‘Numeric’ and ‘Character’ are the two types of Data types which the SAS program contains.
Q #5) What are PDV and it functions?
Answer: Program Data Vector (PDV) is a logical concept and is defined as an area of memory where a data set is being built by SAS.
Functions of PDV are as follows:
- A database having one observation at one time is created.
- The input buffer for holding the data from an external file is created at the time of compilation.
- PDV contains two automatic variables namely, _N_ (displays the count of the data step that is being executed) and _ERROR_ (notifies the error that occurs at the time of execution).
Q #6) What do you know about SAS data set?
Answer: SAS data set is basically referred to as the data that is available for analysis within a SAS program. SAS dataset is also referred to as SAS data table.
SAS data table consists of two parts:
- Columns of variables
- Rows of observations
Useful information about SAS data set can be summarized as follows:
- SAS Dataset can read as well as it has built-in data sources for use like Excel, Access, etc.
- The dataset which is used only in the current session run and discarded after the session ends is known as Temporary Dataset.
- The Dataset that is stored for use in the future session is also known as Permanent Dataset.
- The built-in data set can be accessed using this path Libraries -> My Libraries->SASHELP.
Q #7) Explain why double trailing @@ is used in Input Statement?
Answer: During data step iteration, including double trailing @@ in Input statements implies that SAS should hold the current record for the purpose of execution of next Input statement rather than switching onto the new record.
Q #8) Explain the difference between NODUP and NODUPKEY options?
Answer: For removing duplicate values from the table, PROC SORT is basically categorized between two options:
The difference between these two options can be seen below:
|Compares just the BY variable present in the dataset.||Compares all the variables present in the dataset.|
|Removes duplicate options for the values of variable listed in BY statement.||Identifies and eliminates duplicate observations.|
PROC SORT DATA=readin NODUPKEY;
BY variable name;
PROC SORT DATA=readin NODUP;
BY variable name;
Q #9) Which command is used to perform sorting in SAS program?
Answer: PROC SORT command is used for performing sorting, be it on a single variable or multiple variables. This command is performed on the dataset where the new data set is created as a result of sorting but the original data set remains unchanged.
PROC SORT DATA=original OUT=Sorted;
‘Original’ refers to original dataset
‘Sorted’ refers to the result as sorted dataset
‘Variable’ refers to the column on which sorting operation is done.
Sorting can be done in both ascending as well as descending order.
For the dataset to display in descending order, keyword ‘Descending’ is used in the BY statement with column name on which sorting is to be performed.
PROC SORT DATA=original OUT=Sorted;
BY DESCENDING variable
Q #10) Explain the difference between Informat and Format with an example.
Answer: The difference between Informat and Format can be explained as shown below:
|Indicate SAS how to read data into SAS variable.||Indicate SAS how to display values in the variable.|
|These are used to read the data or take input data from external files.||These are used to write the data.|
Q #11) Differentiate INPUT and INFILE.
Answer: Including an INFILE statement within the SAS programming identifies an external file which consists of the data, whereas including INPUT statement in SAS programming describes the variables used.
The syntax for INFILE:
The syntax for INPUT:
INPUT ‘varname1’ ‘varname2’;
Q #12) Explain the use of PROC print and PROC contents?
Answer: The PROC step of the SAS program is used to invoke built-in procedures for analyzing the data of the dataset.
PROC print: Ensures that the data present in the dataset are read correctly.
PROC contents: Displays the information about SAS dataset.
Q #13) Explain DATA_NULL_?
Answer: As the name defines, DATA_NULL_ is a data step that actually does not create any data set.
It is used for:
- Creating macro variables.
- Writing the output without any data set.
Q #14) How is character variable converted into numeric variable and vice versa?
Answer: Under SAS programming, there arise many tasks where a character value is to be converted into the numeric and in the same way, a numeric value is to be converted into a character value.
PUT() is used to convert numeric to character. In this case, the source format and source variable type must always be similar.
char_var= PUT( num_var, 6.);
INPUT() is used to convert a character to the numeric. In this case, the source variable type must always be character variables.
Q #15) What is the purpose of _CHARACTER_ and _NUMERIC_?
Answer: In the current dataset,
_CHARACTER_ defines all the character variables that are currently defined.
Example: To include all the character variables in PROC MEANS, the following statements are used:
_NUMERIC_ defines all the numeric variables that are currently defined.
Example: To include all the numeric variables in PROC MEANS, following statements are used:
Q #16) What commands are used in the case of including or excluding any specific variables in the data set?
Answer: DROP, KEEP, and data set options are used for this purpose.
The variable we want to remove from the data step is specified in the DROP statement.
The variable we want to retain from the data step is specified in the KEEP statement.
Q #17) Differentiate between PROC MEANS and PROC SUMMARY.
Answer: The difference between PROC MEANS and PROC SUMMARY can be understood as follows:
|PROC MEANS||PROC SUMMARY|
|This procedure produces the printed report by default in the OUTPUT window.||This procedure includes the PRINT in the statement to produce the printed report.|
|PROC MEANS by default take all the numeric variables in the analysis.||PROC SUMMARY takes the variables into the statistical analysis that are described in VAR statement.|
Q #18) Explain the purpose of SUBSTR functions in SAS programming.
Answer: In SAS programming, whenever there is a requirement of the program to abstract a substring, SUBSTR function is used in case of a character variable.
When a start position and length is specified, then this function is used for abstracting character string.
Syntax: SUBSTR(char_var, start,length);
Q #19) Name and describe few SAS character functions that are used for data cleaning in brief.
Answer: Few SAS character functions that are used for data cleaning are enlisted below:
- Compress(char_string) function is used for removing blanks or some specified characters from a given string.
- TRIM(str) function is used for removing trailing blanks from a given string.
- LOWCASE(char_string) function is used for converting all the characters in a given string to lowercase.
- UPCASE(char_string) function is used for converting all the characters in a given string to uppercase.
- COMPBL(str) function is used for converting multiple blanks to a single blank.
Q #20) Mention few ways with which a “table lookup’ is done in SAS programming.
Answer: In SAS programming, the table lookup values can be stored in the following ways:
- Hash object
The following techniques are used to perform ‘table lookup’ in SAS respectively:
- SELECT/WHEN or IF/THEN statements
- Array Index value
- Hash object key value
- FORMAT statement, PUT function
- Merge, join, KEY= Option
Let us see an example which shows the ‘Code’ way to perform table lookup by using ‘IF/THEN’ statements:
if AreaCode=’226′ then Location=’Ontario, Canada’;
else if AreaCode=’212′ then Location=’New York, NY’;
Q #21) Differentiate between CEIL and FlOOR functions.
Answer: CEIL function is used for truncating numeric values where it displays the output as the smallest integer. By smallest integer, here means the integer value is greater than/equal to the argument.
Example: CEIL(12.85) will display output as 13.
FLOOR function is used for truncating numeric values where it displays the output as the greatest integer. By greatest integer, here means that the integer value is less than/equal to the argument.
Example: FLOOR(12.85) will display output as 12.
Q #22) What are the ways in which Macro variables can be created in SAS programming?
Answer: Well a number of different techniques can be used to create macro variables in SAS programming.
Enlisted below are the five most commonly used methods:
- %LET statement
- Macro parameters (named as well as positional)
- %DO statement (iterative)
- INTO in PROC SQL
- CALL SYMPUTX routine
Q #23) Explain the purpose of RETAIN statement.
Answer: As the meaning of the word ‘RETAIN’ signifies to keep the value once assigned, the purpose of RETAIN statement is same in SAS programming as it’s meaning implies.
Within a SAS program, when it is required to move from the current iteration to the next of the data step, at that time RETAIN statement tells SAS to retain the values rather than set them to missing.
Example: Let us print a program which will display the output value of ‘z’ starting from 1 by using the RETAIN statement.
RETAIN z 0;
z = z + 1;
Q #24) Which command is used to save logs in the external file?
Answer: PROC PRINTTO command is used to save logs in the external file.
PROC PRINTTO log=”C:\Users\abc\Downloads\LOG11.txt” new;
Q #25) Mention some common errors that are usually committed in SAS programming.
Answer: Enlisted below are some of the common errors which are usually committed especially when you are new to this programming language.
- The basic syntax includes a semicolon at the end of each statement and missing a semi-colon is the most common mistake.
- You skip checking the logs after submitting the program.
- Commenting errors like failing to use comments where necessary or using comments in an inappropriate way.
- Not using proper debugging methods.
Q #26) Mention SAS system options to debug SAS macros.
Answer: To help in tracking the macro code as well as the SAS code generated by the macros, some system options can be used.
The message that will be generated by these system options can be seen in the SAS log.
Q #27) Differentiate between SAS functions and SAS procedures.
Answer: The major differences can be discovered/understood by the case explained for both SAS functions and Procedures.
The case is that:
For Function, argument value is supplied or say taken for calculation across the observation mentioned in the program statement whereas, in the case of Procedure, every observation is expected to have only one variable through which calculation is done as mentioned in the below example.
Let us understand it with examples:
avgtemp = mean( of T1 – T24 );
Here in the above examples, the arguments passed to the mean function are taken for calculation as an observation.
Here in the above example, Proc means function calculates the average temperature for one argument that is passed as an observation i.e. by month.
Q #28) What do you know about SYMPUT and SYMGET?
Answer: The major differences between the two are mentioned below.
SYMPUT is used for storing the value of a data set into the macro variable whereas SYMGET is used for retrieving the value from the macro variable to the data set.
Q #29) Explain the special input delimiters used in SAS programming.
Answer: The special input delimiters used in SAS programming are:
They are used in the statement ‘INFILE’ and DSD has the functionality of ignoring the delimiters that appear enclosed in quotation marks.
Q #30) Which function is used to count the number of intervals between two SAS dates?
Answer: Interval function INTCK is used for counting the number of intervals between two given SAS dates.
So far, we have seen multiple questions and answers which would have given you a clear understanding of SAS programming concepts as well as given you an idea about the nature of questions being asked in SAS interviews.
Well, if you are new to SAS programming, the knowledge of some technologies of Computer programming and familiarity with SQL (Structured query language) will be an added advantage to you for understanding as well as learn SAS quickly.
Hope you are ready to face any SAS interview confidently!!