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