What's the Execution Order of Components in a SQL SELECT Statement?

Execution Order of SQL Statement Components

In the provided SQL query:

SELECT TOP 5 C.CustomerID,C.CustomerName,C.CustomerSalary
FROM Customer C
WHERE C.CustomerSalary > 10000
ORDER BY C.CustomerSalary DESC

the execution order of the main components is as follows:

1. FROM Clause:
Defines the table(s) from which data will be retrieved. In this case, it is "Customer C".

2. WHERE Clause:
Filters the rows from the selected table based on the specified condition, "C.CustomerSalary > 10000". Only rows satisfying this condition will be considered for further processing.

3. ORDER BY Clause:
Sorts the filtered rows from the WHERE clause in descending order of "C.CustomerSalary" after processing.

4. TOP Clause:
Limits the result set to the top 5 rows sorted by the ORDER BY clause.

Additional Note:

As mentioned in the query documentation, the physical execution order may differ from the logical order described above due to optimizations performed by the query processor. However, the components will always be executed in the general sequence outlined here.

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