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DRDS SQL支持范围__产品简介_分布式关系型数据库 DRDS-阿里云

DRDS支持绝大部分MySQL语法和协议，包括类似SHOW DATABASES, SHOW TABLES, 以及各种DML语句包括SELECT,UPDATE,INSERT,REPLACE, DELETE,UNION等，以及有限的DRDS自定义控制命令. 总体来说，DRDS在常规的DML SQL使用几乎没有限制，但从性能考虑，我们会有一些针对分布式系统的特殊优化方式，如小表复制，如分布式索引，请参阅我们的最佳使用场景.

SQL大类的限制与约束：

  • 暂不支持用户自定义数据类型、自定义函数
  • 暂不支持视图、存储过程、触发器、游标
  • 暂不支持类似 BEGIN…END，LOOP…END LOOP，REPEAT…UNTIL…END REPEAT，WHILE…DO…END WHILE 等的复合语句
  • 暂不支类似 IF,WHILE 等流程控制类语句
  • 全面的DML支持,有限的DDL支持,有限的控制指令支持

下面罗列了目前DRDS支持的SQL语法列表,以mysql的语法列表为蓝本,下面列出的语法代表为已支持,如有特殊说明,代表部分不支持的CASE.

数据库登陆协议

经过测试的客户端: Workbench , Navicat, SQLyog等

数据库DDL语法

数据库DML语法

不支持的语法:

  • 受限于分布式事务
    • 跨分片操作, UPDATE/DELETE [ORDER BY] LIMIT
    • 跨分片操作, UPDATE A,B set A.s = B.s+1 WHERE A.ID = B.NAME , 非拆分字段之间的跨库JOIN
    • 拆分键变更, UPDATE A SET A.ID = 1 WHERE XXX, ID为拆分字段
    • 跨分片操作, INSERT A SELECT B WHERE B.ID > XX , 跨库导入导出数据
    • 跨库事物, 比如两次UPDATE不在一个分片上
  • 子查询限制
    • 暂不支持非where条件的correlate subquery
    • 暂不支持sql中带聚合条件和correlate subquery
  1. 例1:  父查询的select列上存在关联子查询，引用了父查询的a.user_id
  2. select a.user_id , (select sum(score) from b where b.user_id = a.user_id) from a order by a.user_id desc limit 10
  4. 例2:  父查询存在count聚合函数,where条件存在exists的关联子查询引用了a.user_id
  5. select count(*) from a where exists (select * from b where b.user_id = a.user_id and b.score < 60)

数据库事务语法

数据库prepare语法

限制: prepare协议不可与SQL多语句一起混用

数据库管理语法

数据库工具命令

DRDS自定义指令

  • SHOW SEQUENCES / CREATE SEQUENCE / ALTER SEQUENCE / DROP SEQUENCE 【全局sequence管理】
  • SHOW PARTITIONS FROM TABLE 【查询表的拆分字段】
  • SHOW TOPOLOGY FROM TABLE 【查询表的物理拓扑】
  • SHOW BRAODCASTS 【查询所有广播表】
  • SHOW RULE [FROM TABLE] 【查询表拆分定义】
  • SHOW DATASOURCES 【查询后端DB链接池定义】
  • SHOW DBLOCK / RELEASE DBLOCK 【分布式LOCK定义】
  • SHOW NODE 【查询读写库流量】
  • SHOW SLOW 【查询慢SQL列表】
  • SHOW PHYSICAL_SLOW 【查询物理DB执行慢SQL列表】
  • TRACE SQL_STATEMENT / SHOW TRACE 【跟踪SQL执行,profile整个执行过程】
  • EXPLAIN [DETAIL/EXECUTE] SQL_STATEMENT 【分析DRDS执行计划和物理DB上的执行计划】
  • RELOAD USERS 【同步DRDS控制台用户信息到DRDS SERVER】
  • RELOAD SCHEMA 【清理DRDS对应DB库数据缓存,比如SQL解析/语法树/表结构缓存】
  • RELOAD DATASOURCES 【重建后端与所有DB的链接池】

数据库系统函数

整体函数分为解析和执行部分

  • 函数解析: 主要指解析纯SQL中的函数定义,如果函数可以被正常解析,意味着如果用户SQL中带着了拆分字段,函数都可以下发到MySQL上进行执行
  • 函数执行: 主要指用户SQL不能完全下推到MySQL得到结果的情况,需要DRDS层进行二次计算时的函数支持列表.

一个例子理解:

  1. 1. select count(*) from users where user_id = 1;  # user_id为切分条件, count(*)函数主要就是一个SQL解析然后发给MySQL执行,这一类的行为就取决于DRDS的函数解析的支持能力.
  2. 2. select count(*) from users; # 用户SQL未带切分条件, DRDS会对每个分片返回的count结果,在DRDS层面重新计算出一个全局的count(*)结果返回给用户,这一类的行为就取决于DRDS的函数执行的支持能力.

支持范围:

操作符函数

function description
AND, && Logical AND
= Assign a value (as part of a SET statement, or as part of the SET clause in an UPDATE statement)
BETWEEN … AND … Check whether a value is within a range of values
BINARY Cast a string to a binary string
& Bitwise AND
~ Bitwise inversion
^ Bitwise XOR
DIV Integer division
/ Division operator
<=> NULL-safe equal to operator
= Equal operator
>= Greater than or equal operator
> Greater than operator
IS NOT NULL NOT NULL value test
IS NOT Test a value against a boolean
IS NULL NULL value test
IS Test a value against a boolean
<< Left shift
<= Less than or equal operator
< Less than operator
LIKE Simple pattern matching
- Minus operator
%, MOD Modulo operator
NOT BETWEEN … AND … Check whether a value is not within a range of values
!=, <> Not equal operator
NOT LIKE Negation of simple pattern matching
NOT REGEXP Negation of REGEXP
NOT, ! Negates value
OR Logical OR
+ Addition operator
REGEXP Pattern matching using regular expressions
>> Right shift
RLIKE Synonym for REGEXP
* Multiplication operator
- Change the sign of the argument
XOR Logical XOR
Coalesce Return the first non-NULL argument
GREATEST Return the largest argument
LEAST Return the smallest argument
STRCMP Compare two strings

流程控制函数

function description
CASE Case operator
IF() If/else construct
IFNULL() Null if/else construct
NULLIF() Return NULL if expr1 = expr2

字符串函数

function description
ASCII() Return numeric value of left-most character
BIN() Return a string containing binary representation of a number
BIT_LENGTH() Return length of argument in bits
CHAR_LENGTH() Return number of characters in argument
CHAR() Return the character for each integer passed
CHARACTER_LENGTH() Synonym for CHAR_LENGTH()
CONCAT_WS() Return concatenate with separator
CONCAT() Return concatenated string
ELT() Return string at index number
EXPORT_SET() Return a string such that for every bit set in the value bits, you get an on string and for every unset bit, you get an off string
FIELD() Return the index (position) of the first argument in the subsequent arguments
FIND_IN_SET() Return the index position of the first argument within the second argument
FORMAT() Return a number formatted to specified number of decimal places
HEX() Return a hexadecimal representation of a decimal or string value
INSERT() Insert a substring at the specified position up to the specified number of characters
INSTR() Return the index of the first occurrence of substring
LCASE() Synonym for LOWER()
LEFT() Return the leftmost number of characters as specified
LENGTH() Return the length of a string in bytes
LIKE Simple pattern matching
LOCATE() Return the position of the first occurrence of substring
LOWER() Return the argument in lowercase
LPAD() Return the string argument, left-padded with the specified string
LTRIM() Remove leading spaces
MAKE_SET() Return a set of comma-separated strings that have the corresponding bit in bits set
MID() Return a substring starting from the specified position
NOT LIKE Negation of simple pattern matching
NOT REGEXP Negation of REGEXP
OCT() Return a string containing octal representation of a number
OCTET_LENGTH() Synonym for LENGTH()
ORD() Return character code for leftmost character of the argument
POSITION() Synonym for LOCATE()
QUOTE() Escape the argument for use in an SQL statement
REPEAT() Repeat a string the specified number of times
REPLACE() Replace occurrences of a specified string
REVERSE() Reverse the characters in a string
RIGHT() Return the specified rightmost number of characters
RPAD() Append string the specified number of times
RTRIM() Remove trailing spaces
SPACE() Return a string of the specified number of spaces
STRCMP() Compare two strings
SUBSTR() Return the substring as specified
SUBSTRING_INDEX() Return a substring from a string before the specified number of occurrences of the delimiter
SUBSTRING() Return the substring as specified
TRIM() Remove leading and trailing spaces
UCASE() Synonym for UPPER()
UNHEX() Return a string containing hex representation of a number
UPPER() Convert to uppercase

数学函数

function description
ABS() Return the absolute value
ACOS() Return the arc cosine
ASIN() Return the arc sine
ATAN2(),ATAN() Return the arc tangent of the two arguments
ATAN() Return the arc tangent
CEIL() Return the smallest integer value not less than the argument
CEILING() Return the smallest integer value not less than the argument
CONV() Convert numbers between different number bases
COS() Return the cosine
COT() Return the cotangent
CRC32() Compute a cyclic redundancy check value
DEGREES() Convert radians to degrees
DIV Integer division
EXP() Raise to the power of
FLOOR() Return the largest integer value not greater than the argument
LN() Return the natural logarithm of the argument
LOG10() Return the base-10 logarithm of the argument
LOG2() Return the base-2 logarithm of the argument
LOG() Return the natural logarithm of the first argument
MOD() Return the remainder
%, MOD Modulo operator
PI() Return the value of pi
POW() Return the argument raised to the specified power
POWER() Return the argument raised to the specified power
RADIANS() Return argument converted to radians
RAND() Return a random floating-point value
ROUND() Round the argument
SIGN() Return the sign of the argument
SIN() Return the sine of the argument
SQRT() Return the square root of the argument
TAN() Return the tangent of the argument
TRUNCATE() Truncate to specified number of decimal places

时间函数

function description
ADDDATE() Add time values (intervals) to a date value
ADDTIME() Add time
CURDATE() Return the current date
CURRENT_DATE() CURRENT_DATE Synonyms for CURDATE()
CURRENT_TIME() CURRENT_TIME Synonyms for CURTIME()
CURRENT_TIMESTAMP() CURRENT_TIMESTAMP Synonyms for NOW()
CURTIME() Return the current time
DATE_ADD() Add time values (intervals) to a date value
DATE_FORMAT() Format date as specified
DATE_SUB() Subtract a time value (interval) from a date
DATE() Extract the date part of a date or datetime expression
DATEDIFF() Subtract two dates
DAY() Synonym for DAYOFMONTH()
DAYNAME() Return the name of the weekday
DAYOFMONTH() Return the day of the month (0-31)
DAYOFWEEK() Return the weekday index of the argument
DAYOFYEAR() Return the day of the year (1-366)
EXTRACT() Extract part of a date
FROM_DAYS() Convert a day number to a date
FROM_UNIXTIME() Format UNIX timestamp as a date
GET_FORMAT() Return a date format string
HOUR() Extract the hour
LAST_DAY() Return the last day of the month for the argument
LOCALTIME() LOCALTIME Synonym for NOW()
LOCALTIMESTAMP, LOCALTIMESTAMP() Synonym for NOW()
MAKEDATE() Create a date from the year and day of year
MAKETIME() Create time from hour, minute, second
MICROSECOND() Return the microseconds from argument
MINUTE() Return the minute from the argument
MONTH() Return the month from the date passed
MONTHNAME() Return the name of the month
NOW() Return the current date and time
PERIOD_ADD() Add a period to a year-month
PERIOD_DIFF() Return the number of months between periods
QUARTER() Return the quarter from a date argument
SEC_TO_TIME() Converts seconds to ‘HH:MM:SS’ format
SECOND() Return the second (0-59)
STR_TO_DATE() Convert a string to a date
SUBDATE() Synonym for DATE_SUB() when invoked with three arguments
SUBTIME() Subtract times
SYSDATE() Return the time at which the function executes
TIME_FORMAT() Format as time
TIME_TO_SEC() Return the argument converted to seconds
TIME() Extract the time portion of the expression passed
TIMEDIFF() Subtract time
TIMESTAMP() With a single argument, this function returns the date or datetime expression; with two arguments, the sum of the arguments
TIMESTAMPADD() Add an interval to a datetime expression
TIMESTAMPDIFF() Subtract an interval from a datetime expression
UNIX_TIMESTAMP() Return a UNIX timestamp
UTC_DATE() Return the current UTC date
UTC_TIME() Return the current UTC time
UTC_TIMESTAMP() Return the current UTC date and time
WEEKDAY() Return the weekday index
WEEKOFYEAR() Return the calendar week of the date (1-53)
YEAR() Return the year

类型转换函数

function description
BINARY Cast a string to a binary string
CAST() Cast a value as a certain type
CONVERT() Cast a value as a certain type

最后更新：2016-11-23 17:31:06

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