但是前缀索引也有它的坏处:MySQL 不能在 ORDER BY 或 GROUP BY 中使用前缀索引,也不能把它们用作覆盖索引(Covering Index)。 建立前缀索引的语法:ALTER TABLE table_name ADD KEY(column_name(prefix_length)); 3、主键准则 表必须有主键 不使用更新频繁的列 尽量不选择字符串列 不使用UUID MD5 HASH 默认使用...
在pack_header中存在这部分代码:if (reclength > (ulong) file->max_record_length()) /* 右值为 65535 */{ my_error(ER_TOO_BIG_ROWSIZE, /* 这个就是上面的报错信息对应的状态值 */ MYF(0), static_cast(file->max_record_length())); DBUG_RETURN(1);} 重点在于reclength的值是否大于 65535。
column of BTR_EXTERN_LOCAL_STORED_MAX_SIZE bytes. The length can be stored in one byte. If the column were stored externally, the lengths in the clustered index page would be BTR_EXTERN_FIELD_REF_SIZE and 2. */ field_max_size = BTR_EXTERN_LOCAL_STORED_MAX_SIZE; field_ext_max_size ...
column of BTR_EXTERN_LOCAL_STORED_MAX_SIZE bytes. The length can be stored in one byte. If the column were stored externally, the lengths in the clustered index page would be BTR_EXTERN_FIELD_REF_SIZE and 2. */ field_max_size = BTR_EXTERN_LOCAL_STORED_MAX_SIZE; field_ext_max_size ...
因此了解一下reclength的计算过程:1./* sql/unireg.cc:843 */ 2.if (field->offset + data_offset + length > reclength) 3.reclength= field->offset + data_offset + length; 4. 5./* 6.field->offset 的计算方式 7.sql/sql_table.cc:3816 8.*/ 9.while ((sql_field=it++)...
Error 1406: Data too long for column 'name' at row 1 看报错,第一反应,表中字段长度不够了,马上去修改,紧接着又是一个报错: mysql> ALTER TABLE table1 MODIFY namevarchar(1000) NOT NULL DEFAULT '' COMMENT 'xxx'; ERROR 1071 (42000): Specified key was too long; max key length is 3072 ...
length 的计算方式 sql/unireg.cc:833 */length=field->pack_length;/* 这个pack_length就是和字段类型相关,以varchar为例*//* sql/sql_table.cc:3082 */sql_field->sql_type=MYSQL_TYPE_VAR_STRING;sql_field->pack_length=calc_pack_length(sql_field->sql_type,(uint)sql_field->length);关于`calc...
[=] {DEFAULT | 0 | 1}| STATS_SAMPLE_PAGES [=] value| TABLESPACE tablespace_name [STORAGE {DISK | MEMORY}]| UNION =}partition_options:PARTITION BY{ [LINEAR] HASH(expr)| [LINEAR] KEY ALGORITHM={1 | 2}| RANGE{(expr) | COLUMNS(column_list)}| LIST{(expr) | COLUMNS(column_list)}...
mysql>create table varchar_var(idvarchar(75536))charset=latin1;ERROR1074(42000):Columnlength too bigfor column'id'(max=65535);useBLOBorTEXTinstead 1. 2. latin1是一个字符相当于一个字节 mysql>create table extend_char(namechar(1));mysql>insert into extend_char values('的我');ERROR1406(22001...
grantprivilegeson databasename.tablenameto'username'@'host'withgrantoption; 创建一个数据库 方式1: createdatabase 数据库名; 方式2: createdatabaseifnotexists 数据库名default 默认编码集(utf8) 删除一个数据库 方式1: dropdatabase 数据库名