A style guide is a shared coding standard: documented stylistic and technical rules that make a SQL Server data-tier application consistent. It is an architectural practice, not a matter of personal preference. An imperfect common rule is more useful than each developer following a different private rule. section 2.0 section 2.5
The immediate payoff is readable code under pressure. Poorly formatted stored procedures can require substantial time merely to identify the affected database, reformat the query, and understand its intent before troubleshooting can begin. Meaningful names and consistent layout make code easier to inspect and maintain. section 2.1 section 2.7
A useful guide addresses two kinds of decisions:
- Stylistic rules settle recurring presentation choices, such as tabs versus four spaces, semicolon termination, comma placement, JOIN and ON layout, keyword capitalization, and camel case versus Pascal case. section 2.5
- Technical rules constrain risky or inefficient patterns, including cursors, UNION instead of UNION ALL where possible, SELECT *, NOLOCK, and DISTINCT. section 2.5
- Team members, including DBAs writing administrative scripts, follow the same rules. Exceptions to a no-cursor rule can multiply until the standard becomes unenforceable and small workloads grow. section 9.10
- Security-oriented rules can require stored procedure access rather than dynamically built SQL to help protect against SQL injection. section 14.8
Changing style without changing intent
The same SELECT can be formatted with aligned columns and leading commas or with a different indentation and comma convention. Neither presentation is inherently the point; choosing one convention and applying it consistently lets readers focus on the query rather than decode its layout. section 2.5
Listing 2.14 Changing code style
SELECT #1
c.FirstName #1
, c.LastName #1
, o.LineItems #1
FROM dbo.customers c #1
LEFT JOIN dbo.orders o #1
ON c.CustomerID = o.CustomerID #1
WHERE c.CustomerID >= 2 AND c.CustomerID <= 3 #1
AND c.CustomerID <> 2 ; #1
SELECT #2
cust.FirstName, #2
cust.LastName, #2
ord.LineItems #2
FROM dbo.customers cust #2
LEFT JOIN ( #2
SELECT CustomerID, #2
LineItems #2
FROM dbo.Orders #2
) ord ON cust.CustomerID = ord.CustomerID #2
WHERE cust.CustomerID BETWEEN 2 AND 3 AND cust.CustomerID != 2 ; #2
Compare two layouts for one SELECT statement to see which choices a style guide must settle consistently. section 2.5
