How to Use Calculated Fields Effectively in SQL Databases

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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)    |
+----------------------+

Removing Spaces with the Trim() Function

In data management, we often encounter unwanted spacing issues around string values. To solve this problem, SQL offers several trimming functions, namely RTrim(), LTrim(), and Trim(). These functions are very useful for cleaning the data before proceeding with the further process.

RTrim(), LTrim(), and Trim() functions

  • RTrim(): Removes all spaces on the right side of the string.
  • LTrim(): Removes all spaces on the left side of the string.
  • Trim(): Removes all spaces on either side of the string.

These three functions help ensure that the data retrieved from the database is clean and ready to use, especially when performing string joins or calculations.

Use Cases for Data Cleaning

Here’s an example SQL query that uses the RTrim() function to remove unwanted spaces before combining vendor names and vendor countries:

SELECT Concat(RTrim(vend_name), '(', RTrim(vend_country), ')  AS vend_title
FROM vendors
ORDER BY vend_name;

Code Sample Analysis

Concat(RTrim(vend_name), ‘(‘, RTrim(vend_country), ‘)’): In this query, we use RTrim() on the vend_name and vend_country fields to make sure there are no extra spaces at the end of the vendor or country name. This is essential to maintain a neat and professional output format.

Alias: Using AS vend_title, we give this combined result a name, making it easy to reference in the client application.

Output: The result of this query will result in a new column named vend_title that contains a combination of vendor name and country without additional spaces, such as:

+----------------------+
| vend_title           |
+----------------------+
| ACME (USA)          |
| Anvils R Us (USA)   |
| Furball Inc. (USA)  |
| Jet Set (England)    |
| Jouets Et Ours (France) |
| LT Supplies (USA)    |
+----------------------+

Perform Mathematical Calculations with Calculated Fields

In SQL, we can perform various mathematical calculations using basic operators. Here are the most frequently used operators:

  • +: Summing
  • –: Reduction
  • \*: Multiplication
  • /: Distribution

These operators allow us to perform different types of calculations on the data retrieved from the table. We can also use parentheses to set the order of operations in the calculation.

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