缩进

Created: November-22, 2018

没有被广泛接受的标准。每个人都同意的是，将所有内容压缩成一行是不好的：

SELECT d.Name, COUNT(*) AS Employees FROM Departments AS d JOIN Employees AS e ON d.ID = e.DepartmentID WHERE d.Name != 'HR' HAVING COUNT(*) > 10 ORDER BY COUNT(*) DESC;

至少，将每个子句放入一个新行，如果它们变得太长则拆分行：

SELECT d.Name,
       COUNT(*) AS Employees
FROM Departments AS d
JOIN Employees AS e ON d.ID = e.DepartmentID
WHERE d.Name != 'HR'
HAVING COUNT(*) > 10
ORDER BY COUNT(*) DESC;

有时，引入子句的 SQL 关键字之后的所有内容都缩进到同一列：

SELECT   d.Name,
         COUNT(*) AS Employees
FROM     Departments AS d
JOIN     Employees AS e ON d.ID = e.DepartmentID
WHERE    d.Name != 'HR'
HAVING   COUNT(*) > 10
ORDER BY COUNT(*) DESC;

（这也可以在正确对齐 SQL 关键字时完成。）

另一种常见的风格是将重要的关键字放在他们自己的行上：

SELECT
    d.Name,
    COUNT(*) AS Employees
FROM
    Departments AS d
JOIN
    Employees AS e
    ON d.ID = e.DepartmentID
WHERE
    d.Name != 'HR'
HAVING
    COUNT(*) > 10
ORDER BY
    COUNT(*) DESC;

垂直对齐多个相似表达式可提高可读性：

SELECT Model,
       EmployeeID
FROM Cars
WHERE CustomerID = 42
  AND Status     = 'READY';

使用多行会使 SQL 命令更难嵌入到其他编程语言中。但是，许多语言都有多线字符串的机制，例如 C#中的 @"..."，Python 中的 """...""" 或 C++中的 R"(...)"。