例如：varchar和数字类型；根据大多数SQL来创建索引；对于运行较久的大表，需要关注索引字段的区分度问题，当索引值出现了严重倾斜时，需要考虑优化拆分索引值。4.PROFILE分析
但是MySQL不是,它只有CHAR和VARCHAR。需要通过设置字符集来达到存储存储其他字符的目的。 For example, these data type declarations are equivalent: CHAR(10) CHARACTER SET utf8 NATIONAL CHARACTER(10) NCHAR(10) As are these: VARCHAR(10) CHARACTER SET utf8 NATIONAL VARCHAR(10) NCHAR VARCHAR(10) NATIONA...
Yes/NoA logical field can be displayed as Yes/No, True/False, or On/Off. In code, use the constants True and False (equivalent to -1 and 0).Note:Null values are not allowed in Yes/No fields1 bit Ole ObjectCan store pictures, audio, video, or other BLOBs (Binary Large Objects)up...
When a table is created withROW_FORMAT=DYNAMIC,InnoDBcan store long variable-length column values (forVARCHAR,VARBINARY, andBLOBandTEXTtypes) fully off-page, with the clustered index record containing only a 20-byte pointer to the overflow page. Fixed-length fields greater than or equal to 768...
For example,TIME(0),TIME(2),TIME(4), andTIME(6)use 3, 4, 5, and 6 bytes, respectively.TIMEandTIME(0)are equivalent and require the same storage. Storage Requirements for String Types In the following table,Mrepresents the declared column length in characters for nonbinary string types ...
标准的SQL中使用NCHAR,NVARCHAR等表示国际字符集。但是MySQL不是,它只有CHAR和VARCHAR。需要通过设置字符集来达到存储存储其他字符的目的。 For example, these data type declarations are equivalent: CHAR(10) CHARACTER SET utf8 NATIONAL CHARACTER(10)
BTW do you really need all those varchar columns? Why not one varchar and one identity column to indicate whether it's counlimited1, counlimited2, etc. Subject Written By Posted sql server 2005 nvarchar(max) equivalent in mysql? mayank jarsaniya ...
set hg_experimental_enable_double_equivalent=on;--session级别 alter database XXX set hg_experimental_enable_double_equivalent=on;--整个库生效 Union Union要求列的字段类型必须完全匹配。示例如下。 示例代码: SELECT project_id FROM tableA union ALL select project_id from tableB; 问题描述: 如project_...
| MAX_ROWS [=] value | MIN_ROWS [=] value | PACK_KEYS [=] {0 | 1 | DEFAULT} | PASSWORD [=] 'string' | ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT} | STATS_AUTO_RECALC [=] {DEFAULT|0|1} | STATS_PERSISTENT [=] {DEFAULT|0|1} ...
because the two are logically equivalent. Not so in MySQL, which sorts the values in the IN() list and uses a fast binary search to see whether a value is in the list. This is O(Log n) in the size of the list, whereas an equivalent series of OR clauses is O(n) in the size...