Sorting in SQL allows keeping the rows either Ascending or Descending. Two ways the sorting you can. One is with ORDER BY and the other one with DISTINCT.
1. SQL ORDER BY Sorting rows
When you use the ORDER BY clause, the column name on which you are ordering should not be present in the SELECT statement.
Here is an example:
SELECT emp_no, last_name, first_name
FROM emp
ORDER BY work_dept;Here, the work_dept uses for ordering. So it is not given in SELECT. You had better limit the number of columns to participate in the sort. Else, sorting might take longer.
Group By clause
Grouping with SQL is helpful when you want to return aggregate data. Consider the following query:
Here’s an example:
SELECT work_dept, SUM(salary)
FROM emp
GROUP BY work_dept; The output will have work_dept and its aggregate sum of salaries for all the employees in the work_dept. The order of the work_dept is random since it does not use the ORDER BY clause.
2. SQL DISTINCT Sorting rows
The DISTINCT keyword internally does sort, even if there are no duplicate rows. Keep this in mind the overhead for DISTINCT is high.
However, this is not a recommendation to never use it as there may be very valid reasons for doing so.
Having clause
Additionally, the HAVING clause eliminates departments that are of no use.
Here’s an example:
SELECT work_dept, SUM(salary)
FROM emp
GROUP BY work_dept
HAVING AVG(salary) < 5000;Related posts
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