jelovac / mysql-coding-style

Formatting guidelines for MySQL

MySQL coding style

The following document is currently work in progress.

Common

• Language keywords MUST be written in UPPER CASE format.
• Table and column names MUST be written as they are defined in the database.
• Line length MUST not exceed 80 characters in length, everything longer than that MUST be split into multiple lines.
• To ensure better readability main keywords MUST be right aligned and MUST follow the RIVER pattern (https://www.red-gate.com/simple-talk/sql/t-sql-programming/formatting-sql-code-part-second/).

Indentation

• Indentation MUST be performed using spaces and not tabs.
• Indent size MUST be 8 spaces.

Separators

• Separators MUST be placed at the beginning of the line and not at the end.

Note: This is highly opiniated so we might decide later to switch to the oposite.

Aliases

• MUST use the AS keyword.
• MUST be camelCase.

Subqueries and other expressions

• MUST be surrounded with parenthesis.
• MUST be aliased.

Selects

SELECT clause

• Column name MUST be specified inline with the SELECT keyword when selecting a single column.

  Example:

  SELECT birthDate
  

• Column name MUST be specified on a separate line below the SELECT keyword, indented, when selecting multiple columns.

  Example:

  SELECT
          firstName
       ,  lastName
       ,  birthDate
  

FROM clause

• Table name MUST be specified inline with the FROM keyword.
• Table name MUST have an alias when JOIN clauses are defined.
• From clause MUST consist of only one table. Usage of implicit JOIN statements is prohibited.

Example:

SELECT
        person.firstName
     ,  person.lastName
     ,  account.balance
  FROM  people AS person
 INNER
  JOIN  accounting AS account
    ON  account.person_id = person.id

JOIN clause

• Inner join MUST be defined using INNER JOIN keyword, the usage of short JOIN keyword variant is prohibited.
• Left/Right outer joins MUST be defined using LEFT/RIGHT JOIN keyword, the usage of long oboslete LEFT/RIGHT OUTER JOIN keyword is prohibited.
• Joined tables MUST have an alias.

WHERE clause, HAVING clause

• Short conditions SHOULD be specified inline.

  Example:

  WHERE  person.id = 5
  

• The AND/OR operator MUST be positioned at the beginning of the line.

• Long conditions MUST be split over multiple lines.

  Example:

  WHERE
         account.balance IS NULL
         AND person.id = 5
  

• Conditions which have complex logic must be surrounded by parenthesis.

  Example:

  SELECT  MAX(account.balance)
    FROM  people AS person
   INNER
    JOIN  acconting AS account
      ON  account.person_id = person.id
   WHERE
          (
                  YEAR(person.birthDate) >= 2000
             AND  person.firstName = "Nikola"
          )
          OR (
                  MONTH(person.birthDate) = 5
             AND  (
                         account.column_d = 1
                    AND  account.column_e IS NULL
            )
          )
  

GROUP BY clause

• Column name MUST be the same as defined in the SELECT clause.
• Column name MUST be specified inline with the GROUP BY keyword when grouping by a single column.
• Column name MUST be specified separately on a new line, indented below the GROUP BY keyword, when grouping by multiple columns.
• Column separator - COMMA - MUST be positioned after the column and not before.

ORDER BY clause

• Order direction keyword - ASC / DESC - MUST be specified inline with the column name.
• Order direction keyword MUST not be omitted.
• Column name MUST be specified inline with the ORDER BY keyword when ordered by a single column.
• Column name MUST be specified separately on a new line, indented below the ORDER BY keyword, when ordered by multiple columns.
• Column separator - COMMA - MUST be positioned after the column and not before.

LIMIT clause

• Limit value MUST be defined inline with the LIMIT keyword.
• LIMIT clause MUST not contain an OFSET, use OFSET clause for defining one.

OFSET clause

• Ofset value MUST be defined inline with the OFSET keyword.

Inserts

INSERT INTO clause

Example:

INSERT 
  INTO  people (
        firstName
     ,  lastName
     ,  birthDate
  )

VALUES clause

Example:

VALUES (
        'Nikola'
     ,  'Tesla'
     ,  '1856-07-10'
)

Updates

UPDATE clause

• Table name MUST be specified inline with the UPDATE keyword when updating a single table.
• Table name MUST be specified on a separate line, indented, when updating multiple tables.

JOIN clause

• MUST follow the same guidelines as in SELECT statement

SET clause

• Column name MUST be specified inline after the SET keyword when updating a single column.
• Column name MUST be specified in a new row, below the SET keyword, indented, when updating multiple columns.

WHERE clause

• MUST follow the same guidelines as in SELECT statement

Example:

UPDATE  accounting AS account
 INNER
  JOIN  people AS person
    ON  person.id = account.person_id
   SET  account.balance = 0
 WHERE  person.deteted = 1

Deletes

DELETE clause

• Table name MUST be ommited when deleting from a single table
• Table name MUST be specified on a new line, indented, when deleting from multiple tables.
• Table separator - COMMA - MUST be placed after the table name.

FROM clause

• MUST follow the same guidelines as in SELECT statement

JOIN clause

• MUST follow the same guidelines as in SELECT statement

WHERE clause

• MUST follow the same guidelines as in SELECT statement