Added sample split a table by a column.

By Topic/Utility Macros/Split Table by Column.sas

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+/************************************************************************************************
+ SPLIT TABLE BY COLUMN
+    A macro program that splits a table by the unique values of a specified column.
+    Keywords: Macro
+    SAS Versions: SAS 9, SAS Viya
+    Documentation: https://go.documentation.sas.com/doc/en/pgmsascdc/default/mcrolref/titlepage.htm
+    1. Create a macro function called SplitTableByColumn that takes two parameters
+    2. Use PROC SQL to extract all unique values from a specific column in a dataset and store them
+       in a macro variable.
+    3. Use the macro variable created in step 1 to split the input table into multiple datasets.
+    4. End the macro definition.
+    5. Example usage of the macro.
+    Note: This macro does not work if the unique values in the specified column
+          contain spaces or special characters that are not valid in SAS dataset names.
+************************************************************************************************/
+
+/************************************************************************************************
+1. Create a macro function called SplitTableByColumn that takes two parameters:
+   a. input_table: the name of the input dataset to be split.
+   b. split_column: the name of the column whose unique values will determine how the table is split.
+   The macro will create separate datasets for each unique value in the specified column.
+************************************************************************************************/
+%macro SplitTableByColumn(input_table, split_column);
+/************************************************************************************************
+2. use PROC SQL to extract all unique values from a specific column in a dataset and store them
+   in a macro variable.
+   a. proc sql starts a SQL procedure in SAS.
+   b. The noprint option tells SAS not to display the usual output in the results window, as this
+      PROC SQL is only to create macro variables.
+   c. select distinct &split_column selects all unique (distinct) values from &split_column.
+   d. into :unique_values separated by ' ' stores all the resulting unique values as a list in one
+      macro variable called unique_values. The separated by ' ' part means that the values will be
+      joined together in the macro variable, separated by spaces.
+   e. from &input_table; specifies the source table, using the macro variable &input_table to
+      refer to the dataset.
+   f. quit; ends the PROC SQL step.
+************************************************************************************************/
+proc sql noprint;
+    select distinct &split_column into :unique_values separated by ' '
+    from &input_table;
+quit;
+
+/************************************************************************************************
+3. Use the macro variable created in step 1 to split the input table into multiple datasets.
+   a. A data step is used to create separate datasets for each unique value.
+   b. The set statement reads from the input table specified by the macro variable input_table.
+   c. A loop iterates over the list of unique values stored in the macro variable unique_values.
+      It does this by using the %scan function to extract the first to the last unique value,
+      represented by the macro variable sqlobs, which is automatically updated by PROC SQL. It
+      assigns the current unique value to a local scope macro variable called current_value.
+   d. The if statement checks if the current row's value in the macro variable split_column
+      matches the current unique value, and if so, outputs that row to a new dataset named after
+      the unique value.
+************************************************************************************************/
+data &unique_values;
+    set &input_table;
+    %do i=1 %to &sqlobs;
+        %local current_value;
+        %let current_value=%scan(&unique_values, &i);
+        if &split_column = "&current_value" then output &current_value;
+    %end;
+run;
+/************************************************************************************************
+4. End the macro definition.
+   a. The %mend statement marks the end of the macro definition.
+************************************************************************************************/
+%mend SplitTableByColumn;
+
+/************************************************************************************************
+5. Example usage of the macro.
+   a. Call the macro with the input table SASHELP.CARS and split by the Origin
+*************************************************************************************************/
+%SplitTableByColumn(input_table=SASHELP.CARS, split_column=Origin)