In SAS, the MERGE statement is used to combine two or more SAS datasets into a single dataset. There are several options available that can be used with the MERGE statement to control how the merging is performed. Here are some commonly used options:
1. BY: Specifies the variables that are used to match records between the input datasets. This option can take multiple variables.
2. IN: Specifies the input datasets to be merged.
3. OUT: Specifies the output dataset to be created after the merging is done.
4. RENAME: Specifies new names for the variables in the input datasets.
5. DROP: Specifies the variables to be excluded from the output dataset.
6. KEEP: Specifies the variables to be included in the output dataset.
7. UPDATE: Specifies that the input dataset(s) should be updated instead of creating a new output dataset.
8. WHERE: Specifies a subset of records to be included in the output dataset based on a condition.
9. SORTED: Specifies that the input datasets are already sorted by the BY variables, which can speed up the merge process.
10. MATCH: Specifies the type of match to be performed. The options are INNER (default), LEFT, RIGHT, and FULL.
11. NODUPRECS: Specifies that only the first occurrence of a record with a given value of the BY variable(s) is to be included in the output dataset.
12. PREFIX: Specifies a prefix to be added to the names of the variables in the input datasets to avoid naming conflicts.