Example: Modifying Data in a SAS Data Set

The documentation explains the use of the `MODIFY` statement to manage inventory updates. It details how the `DATA Step` interacts with the `Inventory` (master) and `InventoryAdd` (transactions) data sets. By using the automatic variable `_IORC_` with the `%SYSRC` macro, the code distinguishes existing observations (`_SOK`) from new ones (`_DSENMR`). For existing observations, the `REPLACE` statement updates stock quantities and prices. For new observations, the `OUTPUT` statement adds them to the master data set. The flexibility of `MODIFY` is highlighted for its ability to modify a data set without creating a new one, while requiring explicit management of actions (REPLACE or OUTPUT) when these statements are used.

Data Analysis

Type : CREATION_INTERNE

The examples use generated data (datalines) to create the 'Inventory' and 'InventoryAdd' data sets.

1 Code Block

DATA Step Data

Explanation :
This code block creates the two data sets required for the example:
- `Inventory` : The master data set representing the current inventory of a warehouse. It contains information about part number, name, stock, price, and received date.
- `InventoryAdd` : The transaction data set containing updates. It includes new parts to add, stock adjustments (`newStock`), and price changes (`newPrice`) for existing or new items. Dates are read with a specific informat.

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1	DATA Inventory;
2	informat receivedDate date9.;
3	INPUT partNumber $ partName $ stock price receivedDate;
4	DATALINES;
5	K89R seal 34 245.00 07jul2015
6	M4J7 sander 98 45.88 20jun2015
7	LK43 filter 121 10.99 19may2016
8	MN21 brace 43 27.87 10aug2016
9	BC85 clamp 80 9.55 16aug2016
10	NCF3 valve 198 24.50 20mar2016
11	KJ66 cutter 6 19.77 18jun2016
12	UYN7 rod 211 11.55 09sep2016
13	JD03 switch 383 13.99 09jan2017
14	BV1E timer 26 34.50 03aug2017
15	;
16	RUN;
17
18	DATA InventoryAdd;
19	INPUT partNumber $ partName $ newStock newPrice;
20	DATALINES;
21	AA11 hammer 55 32.26
22	BB22 wrench 21 17.35
23	BV1E timer 30 36.50
24	CC33 socket 7 22.19
25	K89R seal 6 247.50
26	KJ66 cutter 10 24.50
27	;
28	RUN;

2 Code Block

PROC SORT / PROC PRINT

Explanation :
These steps sort both data sets by `partNumber` to facilitate matching and visualizing changes. `PROC PRINT` is then used to display the initial content of the `Inventory` and `InventoryAdd` data sets before any modification, allowing a clear comparison of the results after the `MODIFY` operation.

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1	PROC SORT DATA=Inventory; BY partNumber; RUN;
2	PROC SORT DATA=InventoryAdd; BY partNumber; RUN;
3	PROC PRINT DATA=Inventory; title "Inventory"; RUN;
4	PROC PRINT DATA=InventoryAdd; title "InventoryAdd"; RUN;

3 Code Block

DATA Step (MODIFY)

Explanation :
This code block uses the `MODIFY` statement to update the `Inventory` data set based on information from the `InventoryAdd` data set. The `BY partNumber` statement ensures observations are matched. The `SELECT (_IORC_)` clause handles two scenarios:
1. If a matching observation is found (`%SYSRC(_SOK)`), the `stock`, `price`, and `receivedDate` values are updated, then `REPLACE` writes the modified observation. The `receivedDate` is updated because even if it's an existing item, new stock has been received.
2. If no matching observation is found (`%SYSRC(_DSENMR)`), a new observation is created with values from `InventoryAdd`, and `OUTPUT` adds it to the `Inventory` data set. `_ERROR_=0` is used to suppress error messages from the log for new observations.
An `OTHERWISE` block is included to handle unexpected I/O errors. Finally, the `Inventory` data set is sorted and displayed to show the changes.

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1	DATA Inventory;
2	modify Inventory InventoryAdd;
3	BY partNumber;
4	select (_iorc_);
5	/*** The observation exists in the master data set */
6	when (%sysrc(_sok))DO;
7	stock = stock + newStock;
8	price=newPrice;
9	receivedDate = today();
10	replace;
11	END;
12	/*** The observation does not exist in the master data set*/
13	when (%sysrc(_dsenmr)) DO;
14	stock=newStock;
15	price=newPrice;
16	receivedDate=today();
17	OUTPUT;
18	_error_=0;
19	END;
20	otherwise DO;
21	put "An unexpected I/O error has occurred."
22	_error_ = 0;
23	stop;
24	END;
25	END;
26	RUN;
27	PROC SORT DATA=Inventory;
28	BY partNumber;
29	RUN;
30	PROC PRINT DATA=Inventory;
31	title "Modified Inventory Data Set Sorted by partNumber";
32	RUN;
33	QUIT;

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