Mastering Readability: A Guide to Indentation in SQL Statements

Proper indentation visually clarifies the hierarchy and nesting of different sections within an SQL statement. This allows you to easily identify the:

• Main clause: (SELECT, INSERT, UPDATE, DELETE)
• Sub-clauses: (FROM, WHERE, JOIN, GROUP BY, ORDER BY)
• Conditions and expressions: Within sub-clauses

Here's an example to illustrate the difference:

Unformatted:

SELECT customer_name, order_date, 
SUM(order_amount) AS total_amount
FROM orders
WHERE order_date >= '2024-01-01' AND order_date <= '2024-02-28'
GROUP BY customer_name
HAVING total_amount > 1000
ORDER BY total_amount DESC;

Indented:

SELECT
    customer_name,
    order_date,
    SUM(order_amount) AS total_amount
FROM orders
WHERE
    order_date >= '2024-01-01'
    AND order_date <= '2024-02-28'
GROUP BY customer_name
HAVING total_amount > 1000
ORDER BY total_amount DESC;

The indented version clearly shows how the WHERE clause and the conditions within it are nested under the FROM clause. Similarly, the GROUP BY, HAVING, and ORDER BY clauses are visually distinct.

• Indentation level: Consistently use the same number of spaces (2-4) for each level of indentation. Avoid mixing spaces and tabs.
• Main clauses: Start each main clause (SELECT, INSERT, UPDATE, DELETE) on a new line and don't indent it.
• Sub-clauses: Indent each sub-clause (FROM, WHERE, JOIN, etc.) one level further than the previous clause.
• Continuation lines: If a clause needs to be split across multiple lines, indent the continuation lines to the same level as the main line.
• Conditions and expressions: Indent additional levels for further nested conditions or expressions within sub-clauses.
• Closing parenthesis: Align the closing parenthesis of each clause with the beginning of its keyword (e.g., WHERE, HAVING).

• Inconsistent indentation: Using different indentation levels throughout your code can lead to confusion. Stick to a consistent approach and enforce it across your team (if applicable) using code linters or style guides.
• Over-indentation: Excessive indentation can also make the code appear cluttered and hard to read. Aim for a balance between clarity and conciseness.
• Indenting specific elements: Some elements like functions with multiple arguments might benefit from minor adjustments for readability. Use your judgment and prioritize clarity.