Sql Except

SQL except

Created By: chatGPT

EXCEPT is a SQL operator that is used to return all rows from the first SELECT statement that are not present in the second SELECT statement. This is similar to the MINUS operator in other database systems. It is often used when you want to find differences between two sets of results from two tables.

SELECT column1, column2
FROM table1
EXCEPT
SELECT column1, column2
FROM table2;

In this example, the query will return all unique records from table1 that do not exist in table2 based on column1 and column2. For the EXCEPT operator to work, both SELECT statements must have the same number of columns and compatible data types.

SELECT id, name
FROM employees
EXCEPT
SELECT id, name
FROM managers;

If you want to include ORDER BY in an EXCEPT query, you must apply it to the first SELECT statement only. Here’s how you can implement it:

SELECT id, name
FROM departments
ORDER BY name
EXCEPT
SELECT id, name
FROM terminated_employees;

Note that the EXCEPT operator automatically removes duplicates from the results. If you wish to retain duplicate rows in the first SELECT statement, you might want to consider other methods, such as using a LEFT JOIN with a WHERE clause.

SELECT a.id, a.name
FROM departments a
LEFT JOIN terminated_employees b ON a.id = b.id
WHERE b.id IS NULL;