How Can We Avoid Mixing UI Logic and Data Access in SQL Queries?

SQL Anti-Pattern: The Peril of Combining UI Logic and Data Access

SQL, the cornerstone of relational database management, operates under a distinct set of principles that often differ from standard programming practices. Mastering SQL requires adopting new approaches and abandoning ineffective patterns.

One common pitfall is intermingling UI logic with data retrieval. This is evident in queries such as:

<code class="language-sql">SELECT
    FirstName + ' ' + LastName as "Full Name",
    CASE UserRole
        WHEN 2 THEN "Admin"
        WHEN 1 THEN "Moderator"
        ELSE "User"
    END as "User's Role",
    CASE SignedIn
        WHEN 0 THEN "Logged in"
        ELSE "Logged out"
    END as "User signed in?",
    CONVERT(varchar(100), LastSignOn, 101) as "Last Sign On",
    DATEDIFF(day, LastSignOn, GETDATE()) as "Days since last sign on",
    AddrLine1 + ' ' + AddrLine2 + ' ' + AddrLine3 + ' ' +
        City + ', ' + State + ' ' + Zip as "Address",
    'XXX-XX-' + SUBSTRING(
        CONVERT(varchar(9), SSN), 6, 4) as "Social Security #"
FROM Users</code>

This practice often arises from a desire for streamlined data binding to user interfaces, where server-side formatting simplifies client-side presentation. However, this approach creates a fragile architecture, tightly coupling the database and UI layers. Furthermore, it severely limits the reusability of stored procedures.

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