SQL MINUS Function Explained

The MINUS function in SQL is used to subtract the results of the second query from the first query, returning only the rows that appear in the first query. This function is commonly used in Oracle databases, other database systems may not support the MINUS function, but other methods can be used to achieve the same functionality.

For example, suppose we have two tables, A and B, and we want to retrieve rows that exist in table A but not in table B. We can use the MINUS function to achieve this.

SELECT column1, column2
FROM tableA
MINUS
SELECT column1, column2
FROM tableB;

This will return only the rows that appear in tableA. Note that the MINUS function automatically removes duplicates, so it will not return duplicate rows.

It is important to note that the MINUS function can only be used to find the difference between query result sets, and cannot be used to filter multiple conditions within a single query. If multiple conditions need to be filtered within a single query, the WHERE clause or other SQL statements can be used instead.