SQL 兼容性怎么样？

[font=PingFangSC, "]DRDS 高度兼容 MySQL 协议和语法，但由于分布式数据库和单机数据库存在较大的架构差异，存在 SQL 使用限制。相关兼容性和 SQL 限制描述如下。

DRDS SQL 限制



SQL 大类限制

• 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 BEGIN…END、LOOP…END LOOP、REPEAT…UNTIL…END REPEAT、WHILE…DO…END WHILE 等复合语句。
• 暂不支类似 IF ，WHILE 等流程控制类语句。

小语法限制



DDL

• CREATE TABLE tbl_name LIKE old_tbl_name 不支持拆分表。
• CREATE TABLE tbl_name SELECT statement 不支持拆分表。

DML

• 暂不支持 SELECT INTO OUTFILE/INTO DUMPFILE/INTO var_name。
• 暂不支持 INSERT DELAYED Syntax。
• 暂不支持非 WHERE 条件的 Correlate Subquery。
• 暂不支持 SQL 中带聚合条件的 Correlate Subquery。
• 暂不支持 SQL 中对于变量的引用和操作，比如 SET @c=1, @d=@c+1; SELECT @c, @d。

数据库管理

• SHOW WARNINGS Syntax 不支持 LIMIT/COUNT 的组合。
• SHOW ERRORS Syntax 不支持 LIMIT/COUNT 的组合。

DRDS SQL 兼容



协议兼容


DRDS 支持 MySQL Workbench , Navicat For MySQL , SQLyog 等主流客户端。

DDL 语法兼容

• CREATE TABLE Syntax
• CREATE INDEX Syntax
• DROP TABLE Syntax
• DROP INDEX Syntax
• ALTER TABLE Syntax
• TRUNCATE TABLE Syntax

DML 语法兼容

• INSERT Syntax
• REPLACE Syntax
• UPDATE Syntax
• DELETE Syntax
• Subquery Syntax
• Scalar Subquery
• Comparisons Subquery
• Subqueries with ANY, IN, or SOME
• Subqueries with ALL
• Row Subqueries
• Subqueries with EXISTS or NOT EXISTS
• Subqueries in the FROM Clause
• SELECT Syntax

Prepare 语法兼容

• PREPARE Syntax
• EXECUTE Syntax
• DEALLOCATE PREPARE Syntax

数据库管理语法兼容

• SET Syntax
• SHOW Syntax
• SHOW COLUMNS Syntax
• SHOW CREATE TABLE Syntax
• SHOW INDEX
• SHOW TABLES Syntax
• SHOW TABLE STATUS Syntax
• SHOW TABLE STATUS Syntax
• SHOW TABLES Syntax
• SHOW VARIABLES Syntax
• SHOW WARNINGS Syntax
• SHOW ERRORS Syntax
• 其他 SHOW 指令会默认下发到 DB 处理，结果数据没有进行分库数据合并
• KILL ‘PROCESS_ID’ ( DRDS 不支持 KILL QUERY 指令，只支持 KILL ‘PROCESS_ID’ )

数据库工具指令

• DESCRIBE Syntax
• EXPLAIN Syntax
• USE Syntax

DRDS 自定义指令

• SHOW SEQUENCES / CREATE SEQUENCE / ALTER SEQUENCE / DROP SEQUENCE 【 DRDS 全局唯一数字序列管理】
• 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 BROADCASTS 【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 连接池定义】
• 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 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 的连接池】

数据库函数

• 带拆分键的 SQL ，所有 MySQL 函数支持。
• 不带拆分键的 SQL，部分函数支持。

[backcolor=transparent]操作符函数

函数表达式	函数描述
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 value
BINARY	Cast a string to a binary string
&	Bitwise AND
~	Bitwise inversion
^	Bitwise XOR
DIV	Integer division
/	Division operator
<=>	NULL-safe equal to perator
=	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
%,	MODModulo 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

[backcolor=transparent]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

[backcolor=transparent]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
CEILIG()	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	Intger 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

[backcolor=transparent]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

[backcolor=transparent]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

[tr=rgb(239, 251, 255)][td]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
[backcolor=transparent]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