Applied Roots - DBMS Practice Test 2 (SQL query order question)

Question

A SQL query is written in its format as clauses are arranged in a specific sequence and these clauses are executed in different sequence. If we’re writing a query using select, from, where, group by, having, order by, Distinct clauses. 
Then how many clauses are needed to be replaced while writing it’s execution order.

A) 1
B) 2
C) 3
D) 4

Answer 1

In SQL, the clauses are typically executed in the following order:

 

FROM: This clause specifies the table(s) from which the data will be retrieved.

WHERE: The WHERE clause filters the rows based on specified conditions.

GROUP BY: It groups the rows based on one or more columns.

HAVING: The HAVING clause filters the grouped rows based on conditions.

SELECT: This clause selects the columns or expressions to include in the result set.

DISTINCT: It eliminates duplicate rows from the result set.

ORDER BY: The ORDER BY clause sorts the result set based on specified columns.

So, when writing the execution order, you generally follow the order mentioned above. You don't necessarily need to replace any of the clauses, but you need to ensure they are in the correct sequence. However, the SELECT clause can be placed before the FROM clause in some SQL dialects when using subqueries. Other than that exception, the sequence should remain as listed above for a standard SQL query.