Have you ever come across the phrase “SELECT *”? If you have, then you might have also heard that it is not recommended to use it in your SQL queries. In this article, we will discuss why using SELECT * can have several disadvantages and why it is best to avoid it in most cases.
Retrieves Unnecessary Columns and Increases Network Traffic
When you use SELECT *, you are essentially retrieving all the columns from a table. This means that you might be fetching more data than you actually need. This can lead to increased network traffic and slower query performance. It is always better to explicitly specify the columns you require in your SELECT statement.
Leads to Usage of Sub-optimal Execution Plan
Another disadvantage of using SELECT * is that it can lead to the usage of sub-optimal execution plans. The SQL Server query optimizer might not be able to choose the most efficient execution plan when it has to consider all the columns in a table. By specifying the required columns, you can help the optimizer generate a more efficient execution plan.
Difficult to Debug
Using SELECT * can make your queries difficult to debug. When you explicitly list the columns you need, it becomes easier to identify any issues or errors in your query. On the other hand, if you are using SELECT *, it can be challenging to pinpoint the exact cause of a problem.
Quick Tricks to Avoid SELECT *
Now that we understand the disadvantages of using SELECT *, let’s discuss a couple of quick tricks to avoid it. These tricks can help you easily list the column names instead of using SELECT *:
- Drag the columns folder from SQL Server Management Studio to Query Editor
- Right-click on the table name, go to “Script Table As”, then select “SELECT To…” and choose the desired option
By following these tricks, you can quickly and easily list the column names in your query, ensuring that you only retrieve the necessary data.
Is There Ever a Reason to SELECT *?
While there might be rare occasions where you need to retrieve every single column from a table, it is generally recommended to avoid using SELECT *. By explicitly specifying the required columns, you can improve query performance, reduce network traffic, and make your queries easier to debug.
Do you have any thoughts on using SELECT *? If you believe there are valid reasons to use it, please share your insights in the comments below.
For more information on SELECT *, you can refer to the following resources:
- SQL SERVER – Solution – Puzzle – SELECT * vs SELECT COUNT(*)
- SQL SERVER – Puzzle – SELECT * vs SELECT COUNT(*)
- SQL SERVER – SELECT vs. SET Performance Comparison
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