Calculated fields are an important tool in data management for manipulating and presenting data more effectively. This tool allows users to perform calculations directly in SQL queries, obtaining the desired results without changing the data in the table. By using calculated fields, users can save time and resources and increase efficiency in data processing.
Calculated fields are columns that don’t physically exist in a database table, but are dynamically created when a query is executed. This allows users to perform mathematical operations or string manipulations on existing data, generating new values from existing columns.
For example, we can use a calculated field to calculate the total price of multiple items by multiplying the number of items by the price per item and displaying the results in a single query.
The data stored in the table is static information that only changes if there is a manual update. In contrast, the calculation results from calculated fields are dynamic and can change each time a query is executed. This means that calculated fields can provide the latest value based on the current conditions without changing the table’s original data.
For example, if we have columns for price and quantity, we can use calculated fields to calculate the total price directly when querying, instead of storing the total price as separate columns in the table.
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Advantages of Using Calculated Fields
Improve data capture efficiency.
Calculated fields allow users to retrieve processed data directly from the database without the need for additional processing on the client side. This speeds up application response and reduces network load, as only the necessary data is sent.
The efficiency of data processing on the server
Database Management Systems (DBMS) are designed to process data quickly and efficiently. With calculated fields, all calculations are performed on the server, which is usually faster than if it were done on the client. It also reduces the use of client resources, such as CPU and memory, thereby improving the overall performance of the application.
Reduce processing requirements at the client.
With calculated fields, much of the processing that would normally be done by a client application can be moved to the database server. This means that the application does not need to perform calculations or change the data format after retrieving it from the database, which saves time and reduces code complexity.
Simplify queries for specific reports or needs.
Calculated fields allow users to simplify complex queries to be easier to understand and manage. For example, instead of taking multiple separate columns and performing calculations in the app, the user can create a single query with a calculated field that provides the desired final result. This not only improves the readability of queries but also makes it easier to create reports or analyze data.
How to Create Calculated Fields in SQL
Calculated fields are created by adding a formula or function in the SELECT command. This formula can be text merging, number calculation, or other data processing. The result columns of this calculation are not stored in the table but are automatically created when the query is executed.
String Merge with Concat()
One common use of Calculated Fields is to combine strings from multiple columns into one. The Concat() function in SQL is used to combine two or more strings into a single string.
The Concat() function allows us to combine the values of multiple columns. In addition, we can use aliases with US keywords to name the calculated columns to make them more accessible and understandable.
Code Examples
Here’s an example SQL query that uses Concat() to combine the vendor name and vendor country into a single new column named vend_title:
SELECT Concat(vend_name, ' (', vend_country, ')') AS vend_title
FROM vendors
ORDER BY vend_name;Code Sample Analysis
Concat(): In this example, the Concat() function combines three elements:
- The vendor name from the vend_name column.
- Strings in the form of spaces and opening brackets ‘ (‘.
- Country name from vend_country column.
- Cap brackets ‘)’.
Alias: Using AS vend_title, we give the combined result a name, so that the result can be referenced as vend_title in the client application.
Output: The result of this query will result in a new column containing the combination of vendor name and country in the desired format, such as:
+----------------------+
| vend_title |
+----------------------+
| ACME (USA) |
| Anvils R Us (USA) |
| Furball Inc. (USA) |
| Jet Set (England) |
| Jouets Et Ours (France) |
| LT Supplies (USA) |
+----------------------+