limits on mysql，limitsonmysql

limits on mysql，limitsonmysql

1、limits of joins

The maximum number of tables that can be referenced in a single join is 61. This also applies to the number of tables that can be referenced in the definition of a view.
2、表最多可以有多少

MySQL has no limit on the number of tables. The underlying file system may have a limit on the number of files that represent tables. Individual storage engines may impose engine-specific constraints. InnoDB permits up to4 billion tables.

3、表大小限制The effective maximum table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits. 
TheInnoDB storage engine maintainsInnoDB tables within a tablespace that can be created from several files. This enables a table to exceed the maximum individual file size. The tablespace can include raw disk partitions, which permits extremely large tables. The maximum tablespace size is 64TB
You are using aMyISAM table and the space required for the table exceeds what is permitted by the internal pointer size.MyISAM permits data and index files to grow up to 256TB by default, but this limit can be changed up to the maximum permissible size of 65,536TB (2567– 1 bytes)To change the default size limit forMyISAM tables, set the myisam_data_pointer_size, which sets the number of bytes used for internal row pointers. The value is used to set the pointer size for new tables if you do not specify theMAX_ROWS option. The value of myisam_data_pointer_sizecan be from 2 to 7. A value of 4 permits tables up to 4GB; a value of 6 permits tables up to 256TB.
You are using theMEMORY (HEAP) storage engine; in this case you need to increase the value of the max_heap_table_sizesystem variable.