The MINUS operator in SQL is used to subtract the result set of one SELECT statement from the result set of another SELECT statement. The MINUS operator is similar to the EXCEPT operator in some SQL implementations.

The purpose of the MINUS operator is to find the difference between two sets of data. It is useful when you need to compare two tables or two queries and find the rows that are in one result set but not in the other. The MINUS operator returns the unique rows from the first SELECT statement that are not present in the second SELECT statement.

Here is an example of how to use the MINUS operator:

SELECT column1, column2, column3
FROM table1
MINUS
SELECT column1, column2, column3
FROM table2;

In this example, the MINUS operator is used to find the rows in table1 that are not present in table2. The two SELECT statements must return the same number of columns with compatible data types.

The result set of the MINUS operator includes only the columns that are specified in the first SELECT statement (table1 in this case). The result set does not include any duplicate rows, even if there are duplicates in the first SELECT statement.

The MINUS operator is useful for identifying the differences between two tables or queries. It can help you find missing or extra data in a dataset, or identify discrepancies between two sources of data.