PostgreSQL – EXCEPT

ByAdmin

The EXCEPT keyword is used in a query to retrieve distinct rows from the result of the first query that are not present in the result of the second query. In other words, it returns the set difference between the results of two queries.

The basic syntax of the EXCEPT operator is as follows:

SELECT columns FROM table1 EXCEPT SELECT columns FROM table2;

where columns are the columns you want to select from the tables.

and table1 and table2 and the tables you want to query.

Here’s a simple example to illustrate how the EXCEPT operator works. Consider two tables, employees and former_employees, both with a name column:

Table employees:

name
Alice
Bob
Carol
David

Table former_employees:

name
Carol
David

You can use the EXCEPT operator to find the employees who are currently employed but not in the list of former employees:

sqlCopy code

SELECT name FROM employees EXCEPT SELECT name FROM former_employees;

The result would be:

name
Alice
Bob

In this example, the EXCEPT operator retrieves the distinct names from the employees table that are not present in the former_employees table.

The columns selected in both queries must have the same data types, and the order of the columns must match for the EXCEPT operator to work correctly. Also, the EXCEPT operator automatically removes duplicate rows from its result set.

Similar Posts

PostgreSQL – ALL Clause

ByAdmin

The ALL clause is typically used in conjunction with comparison operators to compare a value against all values in a set returned by a subquery.The ALL clause returns TRUE if the condition is satisfied for all values in the set. Here’s the basic syntax of using the ALL clause: SELECT columns FROM table_name WHERE expression…

PostgreSQL – LIKE Operator

ByAdmin

The LIKE operator is used to perform pattern matching on string values. It allows you to retrieve rows from a table where a particular column’s value matches a specified pattern. The LIKE operator is commonly used with wildcard characters to perform flexible searches. The basic syntax of the LIKE operator is as follows: SELECT column1,…