Unlocking Boolean Logic: Mastering T-SQL Techniques for Conditional Outputs

This approach compares the column value with a specific condition and returns TRUE if the condition is met, and FALSE otherwise.

Example:

SELECT ProductID,
       CASE WHEN Price > 100 THEN 1 ELSE 0 END AS IsExpensive
FROM Products;

This code checks the Price column. If the price is greater than 100, the IsExpensive column will be set to TRUE (represented by 1), otherwise it will be FALSE (represented by 0).

Using the ISNULL Function:

This function checks if a column is NULL and returns a specified value if it is. You can leverage this to define a boolean value based on the presence or absence of data.

SELECT CustomerID,
       CASE WHEN ISNULL(Email, '') = '' THEN 0 ELSE 1 END AS HasEmail
FROM Customers;

Here, the code checks the Email column. If it's NULL or an empty string, then HasEmail will be FALSE (0); otherwise, it will be TRUE (1).

Using String Comparison and Conversion:

This method involves comparing the column value with specific strings ("true", "false") and converting the result to a boolean using the CAST function.

SELECT OrderID,
       CAST(CASE WHEN Status = 'Shipped' THEN 'TRUE' ELSE 'FALSE' END AS BIT) AS IsShipped
FROM Orders;

This code checks the Status column. If it's "Shipped", then IsShipped will be TRUE; otherwise, it will be FALSE. Note that BIT is the T-SQL data type for boolean values.

Related Issues and Solutions:

• Data Type Mismatch: Ensure the column data type is compatible with the comparison or conversion being performed. For example, comparing a numeric column with a string value might lead to unexpected results.
• Case Sensitivity: Be mindful of case sensitivity in string comparisons. If necessary, use functions like LOWER or UPPER to ensure consistent matching.