suresh The Difference Between WHERE and HAVING Clauses in T-SQL
When working with T-SQL, it's crucial to understand the distinction between the WHERE and HAVING clauses. The focus keyword "WHERE" and "HAVING" are both used to filter data in a SQL query, but they serve different purposes.
WHERE Clause:
The WHERE clause is used to filter records before any groupings are made in a query. It is applied to individual rows and filters data based on specified conditions. For example, you can use the WHERE clause to retrieve all employees with a salary greater than 50000.
HAVING Clause:
In contrast, the HAVING clause comes into play after the data has been grouped using the GROUP BY clause. It filters aggregated data based on specified conditions. For example, you can use the HAVING clause to retrieve all departments with a total sales amount greater than 100000.
Therefore, the key difference between the WHERE and HAVING clauses is that WHERE filters individual rows, while HAVING filters grouped data.
Understanding when to use each clause is essential for writing efficient and meaningful T-SQL queries.
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