SQL style guide SQL樣式指南

這份文件翻譯自以創用 CC 姓名標示-相同方式分享 4.0 國際 授權條款發布的https://www.sqlstyle.guide，譯文以原文同樣的條款發布。

概要

你可以直接使用這些指導方針，或者 fork 後創建自己的版本——最重要的是選擇一套方針並嚴格遵守它。歡迎透過提交 issue 或 pull request 來提交建議或修復 bug。

為了讓閱讀了Joe Celko 的《SQL ProgrammingStyle》的團隊能更容易采用這套規則，這套原則被設計成與該書的型式相容。本指南在某些領域嚴格一些，在另一些領域寬鬆一些。 當然本指南比 Celko 的書更簡潔一些，因為 Celko 的書包含了一些趣聞和每一條原則背後的理由。

將此文檔的 Markdown format 格式添加到專案程式庫中或將該頁面的鏈接發送給所有項目的參與者要比傳閱實體書容易得多。

Simon Holywell所著的《SQL樣式指南》以創用 CC 姓名標示-相同方式分享 4.0 國際 授權條款發布，改編自https://www.sqlstyle.guide。

一般原則

應該做的事情

SELECT file_hash  -- stored ssdeep hash
  FROM file_system
 WHERE file_name = '.vimrc';

/* Updating the file record after writing to the file */
UPDATE file_system
   SET file_modified_date = '1980-02-22 13:19:01.00000',
       file_size = 209732
 WHERE file_name = '.vimrc';

應避免的事情

命名慣例

一般原則

SELECT first_name
  FROM staff;

表格（Tables）

欄位名（Columns）

別名與關聯名（Aliasing or correlations）

SELECT first_name AS fn
  FROM staff AS s1
  JOIN students AS s2
    ON s2.mentor_id = s1.staff_num;

SELECT SUM(s.monitor_tally) AS monitor_total
  FROM staff AS s;

預存程序（Stored procedures）

統一的後綴（Uniform suffix）

下列後綴有統一的意義，能保證 SQL 程式碼更容易被理解。在合適的時候使用正確的後綴。

查詢語句（Query syntax）

保留字（Reserved words）

保留字總是大寫，如 SELECT 和 WHERE。

最好使用保留字的全稱而不是簡寫，用 ABSOLUTE 而不用 ABS。

當標準 ANSI SQL 關鍵字能完成相同的事情時，不要使用資料庫伺服器相依的關鍵字，這樣能增強可移植性。

SELECT model_num
  FROM phones AS p
 WHERE p.release_date > '2014-09-30';

空白字元（White space）

正確地使用空白字元對清晰的程式碼十分重要。不要把程式碼堆在一起或移除自然語言中的空格。

空格（Spaces）

用空格使根關鍵字都結束在同一列上。在程式碼中形成一個從上到下的「川流」，這樣幫助讀者快速掃描程式碼並將關鍵字和實做細節分開。川流在排版時應該避免，但是對書寫 SQL 語句是有幫助的。

(SELECT f.species_name,
        AVG(f.height) AS average_height, AVG(f.diameter) AS average_diameter
   FROM flora AS f
  WHERE f.species_name = 'Banksia'
     OR f.species_name = 'Sheoak'
     OR f.species_name = 'Wattle'
  GROUP BY f.species_name, f.observation_date)

  UNION ALL

(SELECT b.species_name,
        AVG(b.height) AS average_height, AVG(b.diameter) AS average_diameter
   FROM botanic_garden_flora AS b
  WHERE b.species_name = 'Banksia'
     OR b.species_name = 'Sheoak'
     OR b.species_name = 'Wattle'
  GROUP BY b.species_name, b.observation_date);

注意 WHERE 和 FROM 等關鍵字，都靠右對齊，而真實的列名都靠左對齊。

下列是需要加入空格的情況：

SELECT a.title, a.release_date, a.recording_date
  FROM albums AS a
 WHERE a.title = 'Charcoal Lane'
    OR a.title = 'The New Danger';

換行（Line spacing）

必需換行的時機：

將所有的關鍵字右對齊，將所有的值靠左對齊，並在查詢語句中間留出一個空隙。這樣能提高程式碼的閱讀速度。

INSERT INTO albums (title, release_date, recording_date)
VALUES ('Charcoal Lane', '1990-01-01 01:01:01.00000', '1990-01-01 01:01:01.00000'),
       ('The New Danger', '2008-01-01 01:01:01.00000', '1990-01-01 01:01:01.00000');

UPDATE albums
   SET release_date = '1990-01-01 01:01:01.00000'
 WHERE title = 'The New Danger';

SELECT a.title,
       a.release_date, a.recording_date, a.production_date -- grouped dates together
  FROM albums AS a
 WHERE a.title = 'Charcoal Lane'
    OR a.title = 'The New Danger';

縮排（Indentation）

為確保 SQL 的可讀性，務必要遵守下列規則。

Join 語句

Join 語句應該縮進到川流的另一側並在必要的時候加入換行。

SELECT r.last_name
  FROM riders AS r
       INNER JOIN bikes AS b
       ON r.bike_vin_num = b.vin_num
          AND b.engine_tally > 2

       INNER JOIN crew AS c
       ON r.crew_chief_last_name = c.last_name
          AND c.chief = 'Y';

子查詢（Subqueries）

子查詢應該在川流的右側對齊並使用其他查詢相同的樣式。有時候將右括號單獨置於一行並同與它配對的左括號對齊是有意義的——尤其是當存在嵌套子查詢的時候。

SELECT r.last_name,
       (SELECT MAX(YEAR(championship_date))
          FROM champions AS c
         WHERE c.last_name = r.last_name
           AND c.confirmed = 'Y') AS last_championship_year
  FROM riders AS r
 WHERE r.last_name IN
       (SELECT c.last_name
          FROM champions AS c
         WHERE YEAR(championship_date) > '2008'
           AND c.confirmed = 'Y');

推薦的形式（Preferred formalisms）

SELECT CASE postcode
       WHEN 'BN1' THEN 'Brighton'
       WHEN 'EH1' THEN 'Edinburgh'
       END AS city
  FROM office_locations
 WHERE country = 'United Kingdom'
   AND opening_time BETWEEN 8 AND 9
   AND postcode IN ('EH1', 'BN1', 'NN1', 'KW1');

建立語句（Create syntax）

聲明模式信息時維護可讀程式碼也很重要。所以列定義的順序和分組一定要有意義。

在 CREATE 語句中，其後每列要縮排 4 個空格。

選擇數據類型（Choosing data types）

指定預設類型（Specifying default values）

約束和鍵（Constraints and keys）

約束（Constraints）和鍵（key）是構成資料庫系統的重要組成部分。它們能很快地變得難以閱讀和理解，所以遵從指南方針是很重要的。

選擇鍵（Choosing keys）

設計時應該謹慎選擇構成鍵的列，因為鍵既明顯影響著性能和數據完整性。

  1. 鍵在某種程度上應該是獨一無二的。
  2. 該值在不同表中的類型應該相同並且盡量不會更改。
  3. 該值是否會無法通過某些標準格式（如 ISO 發布的標準）？ 遵守第2點。
  4. 盡量讓鍵保持簡單，但在適當情況下不要害怕使用複合鍵。

以上是定義資料庫時合乎邏輯的平衡做法。當需求變更時，鍵也應該根據情況更新。

定義約束（Defining constraints）

確定鍵後，就可以用約束和字值段驗證來定義它們。

概要（General）
布局和順序（Layout and order）
校驗（Layout and order）
範例
CREATE TABLE staff (
    PRIMARY KEY (staff_num),
    staff_num      INT(5)       NOT NULL,
    first_name     VARCHAR(100) NOT NULL,
    pens_in_drawer INT(2)       NOT NULL,
                   CONSTRAINT pens_in_drawer_range
                   CHECK(pens_in_drawer BETWEEN 1 AND 99)
);

Designs to avoid

附錄

保留字參考

下表包含了 ANSI SQL（92, 99 和 2003）、MySQL 3 到 5.x、PostgreSQL 8.1、MS SQL Server 2000、MS ODBC 和 Oracle 10.2 中的關鍵字。

A
ABORT
ABS
ABSOLUTE
ACCESS
ACTION
ADA
ADD
ADMIN
AFTER
AGGREGATE
ALIAS
ALL
ALLOCATE
ALSO
ALTER
ALWAYS
ANALYSE
ANALYZE
AND
ANY
ARE
ARRAY
AS
ASC
ASENSITIVE
ASSERTION
ASSIGNMENT
ASYMMETRIC
AT
ATOMIC
ATTRIBUTE
ATTRIBUTES
AUDIT
AUTHORIZATION
AUTO_INCREMENT
AVG
AVG_ROW_LENGTH
BACKUP
BACKWARD
BEFORE
BEGIN
BERNOULLI
BETWEEN
BIGINT
BINARY
BIT
BIT_LENGTH
BITVAR
BLOB
BOOL
BOOLEAN
BOTH
BREADTH
BREAK
BROWSE
BULK
BY
C
CACHE
CALL
CALLED
CARDINALITY
CASCADE
CASCADED
CASE
CAST
CATALOG
CATALOG_NAME
CEIL
CEILING
CHAIN
CHANGE
CHAR
CHAR_LENGTH
CHARACTER
CHARACTER_LENGTH
CHARACTER_SET_CATALOG
CHARACTER_SET_NAME
CHARACTER_SET_SCHEMA
CHARACTERISTICS
CHARACTERS
CHECK
CHECKED
CHECKPOINT
CHECKSUM
CLASS
CLASS_ORIGIN
CLOB
CLOSE
CLUSTER
CLUSTERED
COALESCE
COBOL
COLLATE
COLLATION
COLLATION_CATALOG
COLLATION_NAME
COLLATION_SCHEMA
COLLECT
COLUMN
COLUMN_NAME
COLUMNS
COMMAND_FUNCTION
COMMAND_FUNCTION_CODE
COMMENT
COMMIT
COMMITTED
COMPLETION
COMPRESS
COMPUTE
CONDITION
CONDITION_NUMBER
CONNECT
CONNECTION
CONNECTION_NAME
CONSTRAINT
CONSTRAINT_CATALOG
CONSTRAINT_NAME
CONSTRAINT_SCHEMA
CONSTRAINTS
CONSTRUCTOR
CONTAINS
CONTAINSTABLE
CONTINUE
CONVERSION
CONVERT
COPY
CORR
CORRESPONDING
COUNT
COVAR_POP
COVAR_SAMP
CREATE
CREATEDB
CREATEROLE
CREATEUSER
CROSS
CSV
CUBE
CUME_DIST
CURRENT
CURRENT_DATE
CURRENT_DEFAULT_TRANSFORM_GROUP
CURRENT_PATH
CURRENT_ROLE
CURRENT_TIME
CURRENT_TIMESTAMP
CURRENT_TRANSFORM_GROUP_FOR_TYPE
CURRENT_USER
CURSOR
CURSOR_NAME
CYCLE
DATA
DATABASE
DATABASES
DATE
DATETIME
DATETIME_INTERVAL_CODE
DATETIME_INTERVAL_PRECISION
DAY
DAY_HOUR
DAY_MICROSECOND
DAY_MINUTE
DAY_SECOND
DAYOFMONTH
DAYOFWEEK
DAYOFYEAR
DBCC
DEALLOCATE
DEC
DECIMAL
DECLARE
DEFAULT
DEFAULTS
DEFERRABLE
DEFERRED
DEFINED
DEFINER
DEGREE
DELAY_KEY_WRITE
DELAYED
DELETE
DELIMITER
DELIMITERS
DENSE_RANK
DENY
DEPTH
DEREF
DERIVED
DESC
DESCRIBE
DESCRIPTOR
DESTROY
DESTRUCTOR
DETERMINISTIC
DIAGNOSTICS
DICTIONARY
DISABLE
DISCONNECT
DISK
DISPATCH
DISTINCT
DISTINCTROW
DISTRIBUTED
DIV
DO
DOMAIN
DOUBLE
DROP
DUAL
DUMMY
DUMP
DYNAMIC
DYNAMIC_FUNCTION
DYNAMIC_FUNCTION_CODE
EACH
ELEMENT
ELSE
ELSEIF
ENABLE
ENCLOSED
ENCODING
ENCRYPTED
END
END-EXEC
ENUM
EQUALS
ERRLVL
ESCAPE
ESCAPED
EVERY
EXCEPT
EXCEPTION
EXCLUDE
EXCLUDING
EXCLUSIVE
EXEC
EXECUTE
EXISTING
EXISTS
EXIT
EXP
EXPLAIN
EXTERNAL
EXTRACT
FALSE
FETCH
FIELDS
FILE
FILLFACTOR
FILTER
FINAL
FIRST
FLOAT
FLOAT4
FLOAT8
FLOOR
FLUSH
FOLLOWING
FOR
FORCE
FOREIGN
FORTRAN
FORWARD
FOUND
FREE
FREETEXT
FREETEXTTABLE
FREEZE
FROM
FULL
FULLTEXT
FUNCTION
FUSION
G
GENERAL
GENERATED
GET
GLOBAL
GO
GOTO
GRANT
GRANTED
GRANTS
GREATEST
GROUP
GROUPING
HANDLER
HAVING
HEADER
HEAP
HIERARCHY
HIGH_PRIORITY
HOLD
HOLDLOCK
HOST
HOSTS
HOUR
HOUR_MICROSECOND
HOUR_MINUTE
HOUR_SECOND
IDENTIFIED
IDENTITY
IDENTITY_INSERT
IDENTITYCOL
IF
IGNORE
ILIKE
IMMEDIATE
IMMUTABLE
IMPLEMENTATION
IMPLICIT
IN
INCLUDE
INCLUDING
INCREMENT
INDEX
INDICATOR
INFILE
INFIX
INHERIT
INHERITS
INITIAL
INITIALIZE
INITIALLY
INNER
INOUT
INPUT
INSENSITIVE
INSERT
INSERT_ID
INSTANCE
INSTANTIABLE
INSTEAD
INT
INT1
INT2
INT3
INT4
INT8
INTEGER
INTERSECT
INTERSECTION
INTERVAL
INTO
INVOKER
IS
ISAM
ISNULL
ISOLATION
ITERATE
JOIN
K
KEY
KEY_MEMBER
KEY_TYPE
KEYS
KILL
LANCOMPILER
LANGUAGE
LARGE
LAST
LAST_INSERT_ID
LATERAL
LEADING
LEAST
LEAVE
LEFT
LENGTH
LESS
LEVEL
LIKE
LIMIT
LINENO
LINES
LISTEN
LN
LOAD
LOCAL
LOCALTIME
LOCALTIMESTAMP
LOCATION
LOCATOR
LOCK
LOGIN
LOGS
LONG
LONGBLOB
LONGTEXT
LOOP
LOW_PRIORITY
LOWER
M
MAP
MATCH
MATCHED
MAX
MAX_ROWS
MAXEXTENTS
MAXVALUE
MEDIUMBLOB
MEDIUMINT
MEDIUMTEXT
MEMBER
MERGE
MESSAGE_LENGTH
MESSAGE_OCTET_LENGTH
MESSAGE_TEXT
METHOD
MIDDLEINT
MIN
MIN_ROWS
MINUS
MINUTE
MINUTE_MICROSECOND
MINUTE_SECOND
MINVALUE
MLSLABEL
MOD
MODE
MODIFIES
MODIFY
MODULE
MONTH
MONTHNAME
MORE
MOVE
MULTISET
MUMPS
MYISAM
NAME
NAMES
NATIONAL
NATURAL
NCHAR
NCLOB
NESTING
NEW
NEXT
NO
NO_WRITE_TO_BINLOG
NOAUDIT
NOCHECK
NOCOMPRESS
NOCREATEDB
NOCREATEROLE
NOCREATEUSER
NOINHERIT
NOLOGIN
NONCLUSTERED
NONE
NORMALIZE
NORMALIZED
NOSUPERUSER
NOT
NOTHING
NOTIFY
NOTNULL
NOWAIT
NULL
NULLABLE
NULLIF
NULLS
NUMBER
NUMERIC
OBJECT
OCTET_LENGTH
OCTETS
OF
OFF
OFFLINE
OFFSET
OFFSETS
OIDS
OLD
ON
ONLINE
ONLY
OPEN
OPENDATASOURCE
OPENQUERY
OPENROWSET
OPENXML
OPERATION
OPERATOR
OPTIMIZE
OPTION
OPTIONALLY
OPTIONS
OR
ORDER
ORDERING
ORDINALITY
OTHERS
OUT
OUTER
OUTFILE
OUTPUT
OVER
OVERLAPS
OVERLAY
OVERRIDING
OWNER
PACK_KEYS
PAD
PARAMETER
PARAMETER_MODE
PARAMETER_NAME
PARAMETER_ORDINAL_POSITION
PARAMETER_SPECIFIC_CATALOG
PARAMETER_SPECIFIC_NAME
PARAMETER_SPECIFIC_SCHEMA
PARAMETERS
PARTIAL
PARTITION
PASCAL
PASSWORD
PATH
PCTFREE
PERCENT
PERCENT_RANK
PERCENTILE_CONT
PERCENTILE_DISC
PLACING
PLAN
PLI
POSITION
POSTFIX
POWER
PRECEDING
PRECISION
PREFIX
PREORDER
PREPARE
PREPARED
PRESERVE
PRIMARY
PRINT
PRIOR
PRIVILEGES
PROC
PROCEDURAL
PROCEDURE
PROCESS
PROCESSLIST
PUBLIC
PURGE
QUOTE
RAID0
RAISERROR
RANGE
RANK
RAW
READ
READS
READTEXT
REAL
RECHECK
RECONFIGURE
RECURSIVE
REF
REFERENCES
REFERENCING
REGEXP
REGR_AVGX
REGR_AVGY
REGR_COUNT
REGR_INTERCEPT
REGR_R2
REGR_SLOPE
REGR_SXX
REGR_SXY
REGR_SYY
REINDEX
RELATIVE
RELEASE
RELOAD
RENAME
REPEAT
REPEATABLE
REPLACE
REPLICATION
REQUIRE
RESET
RESIGNAL
RESOURCE
RESTART
RESTORE
RESTRICT
RESULT
RETURN
RETURNED_CARDINALITY
RETURNED_LENGTH
RETURNED_OCTET_LENGTH
RETURNED_SQLSTATE
RETURNS
REVOKE
RIGHT
RLIKE
ROLE
ROLLBACK
ROLLUP
ROUTINE
ROUTINE_CATALOG
ROUTINE_NAME
ROUTINE_SCHEMA
ROW
ROW_COUNT
ROW_NUMBER
ROWCOUNT
ROWGUIDCOL
ROWID
ROWNUM
ROWS
RULE
SAVE
SAVEPOINT
SCALE
SCHEMA
SCHEMA_NAME
SCHEMAS
SCOPE
SCOPE_CATALOG
SCOPE_NAME
SCOPE_SCHEMA
SCROLL
SEARCH
SECOND
SECOND_MICROSECOND
SECTION
SECURITY
SELECT
SELF
SENSITIVE
SEPARATOR
SEQUENCE
SERIALIZABLE
SERVER_NAME
SESSION
SESSION_USER
SET
SETOF
SETS
SETUSER
SHARE
SHOW
SHUTDOWN
SIGNAL
SIMILAR
SIMPLE
SIZE
SMALLINT
SOME
SONAME
SOURCE
SPACE
SPATIAL
SPECIFIC
SPECIFIC_NAME
SPECIFICTYPE
SQL
SQL_BIG_RESULT
SQL_BIG_SELECTS
SQL_BIG_TABLES
SQL_CALC_FOUND_ROWS
SQL_LOG_OFF
SQL_LOG_UPDATE
SQL_LOW_PRIORITY_UPDATES
SQL_SELECT_LIMIT
SQL_SMALL_RESULT
SQL_WARNINGS
SQLCA
SQLCODE
SQLERROR
SQLEXCEPTION
SQLSTATE
SQLWARNING
SQRT
SSL
STABLE
START
STARTING
STATE
STATEMENT
STATIC
STATISTICS
STATUS
STDDEV_POP
STDDEV_SAMP
STDIN
STDOUT
STORAGE
STRAIGHT_JOIN
STRICT
STRING
STRUCTURE
STYLE
SUBCLASS_ORIGIN
SUBLIST
SUBMULTISET
SUBSTRING
SUCCESSFUL
SUM
SUPERUSER
SYMMETRIC
SYNONYM
SYSDATE
SYSID
SYSTEM
SYSTEM_USER
TABLE
TABLE_NAME
TABLES
TABLESAMPLE
TABLESPACE
TEMP
TEMPLATE
TEMPORARY
TERMINATE
TERMINATED
TEXT
TEXTSIZE
THAN
THEN
TIES
TIME
TIMESTAMP
TIMEZONE_HOUR
TIMEZONE_MINUTE
TINYBLOB
TINYINT
TINYTEXT
TO
TOAST
TOP
TOP_LEVEL_COUNT
TRAILING
TRAN
TRANSACTION
TRANSACTION_ACTIVE
TRANSACTIONS_COMMITTED
TRANSACTIONS_ROLLED_BACK
TRANSFORM
TRANSFORMS
TRANSLATE
TRANSLATION
TREAT
TRIGGER
TRIGGER_CATALOG
TRIGGER_NAME
TRIGGER_SCHEMA
TRIM
TRUE
TRUNCATE
TRUSTED
TSEQUAL
TYPE
UESCAPE
UID
UNBOUNDED
UNCOMMITTED
UNDER
UNDO
UNENCRYPTED
UNION
UNIQUE
UNKNOWN
UNLISTEN
UNLOCK
UNNAMED
UNNEST
UNSIGNED
UNTIL
UPDATE
UPDATETEXT
UPPER
USAGE
USE
USER
USER_DEFINED_TYPE_CATALOG
USER_DEFINED_TYPE_CODE
USER_DEFINED_TYPE_NAME
USER_DEFINED_TYPE_SCHEMA
USING
UTC_DATE
UTC_TIME
UTC_TIMESTAMP
VACUUM
VALID
VALIDATE
VALIDATOR
VALUE
VALUES
VAR_POP
VAR_SAMP
VARBINARY
VARCHAR
VARCHAR2
VARCHARACTER
VARIABLE
VARIABLES
VARYING
VERBOSE
VIEW
VOLATILE
WAITFOR
WHEN
WHENEVER
WHERE
WHILE
WIDTH_BUCKET
WINDOW
WITH
WITHIN
WITHOUT
WORK
WRITE
WRITETEXT
X509
XOR
YEAR
YEAR_MONTH
ZEROFILL
ZONE