proper case function in ansi sql

3 min read 24-10-2024

When it comes to data manipulation in SQL, ensuring that string data is presented in a readable format can be crucial. One common formatting need is transforming strings into 'Proper Case'—where the first letter of each word is capitalized, and all other letters are in lowercase. This article delves into how to achieve proper case in ANSI SQL, common methods used, and best practices.

What is Proper Case?

Proper case, also known as title case, is a text formatting style that capitalizes the first letter of each significant word in a sentence while keeping the rest of the letters in lowercase. For instance:

Proper Case: "This Is An Example Sentence"
Incorrect Case: "this is an example sentence"

Why Use Proper Case?

Proper case is often preferred in applications like:

User interface text (e.g., form fields, menus)
Titles and headings
Professional documents

How to Implement Proper Case in ANSI SQL

Using SQL Functions

ANSI SQL does not have a built-in PROPER() function, which means that achieving proper case will require a combination of string functions. Here’s how to implement it using LOWER() and UPPER(), as well as techniques to capitalize the first letter of each word.

Example SQL Code

Here's a sample implementation for a SQL database that doesn't directly support a proper case function:

WITH SampleData AS (
    SELECT 'hello world' AS original_string
    UNION ALL
    SELECT 'sql is great'
    UNION ALL
    SELECT 'THIS IS AN EXAMPLE'
)
SELECT
    original_string,
    CONCAT(
        UPPER(SUBSTRING(original_string, 1, 1)), 
        LOWER(SUBSTRING(original_string, 2))
    ) AS proper_case_example
FROM SampleData;

Explanation

WITH SampleData AS (...): This Common Table Expression (CTE) creates a temporary dataset to work with.
UPPER(SUBSTRING(original_string, 1, 1)): This part capitalizes the first letter of the string.
LOWER(SUBSTRING(original_string, 2)): This transforms the rest of the string into lowercase.
CONCAT(...): Combines the capitalized first letter with the rest of the string.

Limitations

While the above example is straightforward, it does not handle multiple words correctly. Proper case should capitalize the first letter of each significant word. Therefore, a more complex implementation would be necessary.

Advanced Proper Case Handling

For more comprehensive proper case handling that deals with multiple words, a user-defined function (UDF) or a more complex SQL logic would be needed. Below is an advanced approach:

CREATE FUNCTION ProperCase(@InputString NVARCHAR(255))
RETURNS NVARCHAR(255)
AS
BEGIN
    DECLARE @OutputString NVARCHAR(255) = '';
    DECLARE @CurrentChar NCHAR(1);
    DECLARE @Index INT = 1;

    WHILE @Index <= LEN(@InputString)
    BEGIN
        SET @CurrentChar = SUBSTRING(@InputString, @Index, 1);
        
        IF @Index = 1 OR SUBSTRING(@InputString, @Index - 1, 1) = ' '
        BEGIN
            SET @OutputString = @OutputString + UPPER(@CurrentChar);
        END
        ELSE
        BEGIN
            SET @OutputString = @OutputString + LOWER(@CurrentChar);
        END
        
        SET @Index = @Index + 1;
    END
    
    RETURN @OutputString;
END

Explanation of UDF

CREATE FUNCTION: This command defines a new user-defined function.
WHILE loop: Iterates through each character in the input string.
IF condition: Checks if the current character is the start of the string or follows a space, capitalizing it accordingly.

Practical Example of UDF Usage

After creating the function, you can use it in your SQL queries as follows:

SELECT dbo.ProperCase('this is an example sentence') AS ProperCased;

This will output:

ProperCased
------------
This Is An Example Sentence

Best Practices for Using Proper Case

Understand the Data Context: Determine whether proper casing is necessary for your dataset. Sometimes all uppercase or lowercase may be more appropriate.
Performance Considerations: Keep in mind that using UDFs can impact performance, especially with large datasets.
Consistent Formatting: Maintain consistent formatting throughout your database and applications for a professional appearance.
Testing: Always test your functions with a variety of input cases to ensure accuracy.

Conclusion

Proper casing strings in ANSI SQL is not a straightforward process due to the absence of a built-in function. However, with the use of string manipulation functions and user-defined functions, you can effectively format your string data. Understanding the correct methods and applying them correctly can significantly enhance the readability and professionalism of your database outputs.

References

Original authors on GitHub for SQL Functions.
Additional reading and documentation on ANSI SQL string functions.

Feel free to use and adapt the examples provided to fit your specific database needs, and consider implementing proper case formatting where it adds value to your data presentation!