SQL WITH code example

Example 1: with in sql server

Specifies a temporary named result set, known as a common table expression (CTE). This is derived from a simple query and defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE or MERGE statement. This clause can also be used in a CREATE VIEW statement as part of its defining SELECT statement. A common table expression can include references to itself. This is referred to as a recursive common table expression.
-- Define the CTE expression name and column list.  
WITH Sales_CTE (SalesPersonID, SalesOrderID, SalesYear)  
AS  
-- Define the CTE query.  
(  
    SELECT SalesPersonID, SalesOrderID, YEAR(OrderDate) AS SalesYear  
    FROM Sales.SalesOrderHeader  
    WHERE SalesPersonID IS NOT NULL  
)  
-- Define the outer query referencing the CTE name.  
SELECT SalesPersonID, COUNT(SalesOrderID) AS TotalSales, SalesYear  
FROM Sales_CTE  
GROUP BY SalesYear, SalesPersonID  
ORDER BY SalesPersonID, SalesYear;

Example 2: sql in

Used alongside a WHERE clause as a shorthand for multiple OR conditions.
So instead of:
SELECT * FROM users
WHERE country = 'USA' OR country = 'United Kingdom' OR
country = 'Russia' OR country = 'Australia';
You can use:
SELECT * FROM users
WHERE country IN ('USA', 'United Kingdom', 'Russia',
'Australia');