获取 MySQL 中表的行数?
谁能告诉我在 MySQL 中查找表的行数时哪种方法更好:是
SELECT COUNT(*) FROM TABLE_NAME
在 TABLE
中的表 TABLE
中查找行数 更好? >INFORMATION_SCHEMA?
这会是计算页面分页计数的频繁操作吗?
我应该补充一点,表最多只有几千行。
谢谢马丁
·奥谢。
Can anyone tell me which is he better appraoch in MySQL whin it comes to finding the row count of a table: is it better to do
SELECT COUNT(*) FROM TABLE_NAME
or to look up the row count in the table TABLE
in the INFORMATION_SCHEMA
?
This would be a frequent operation for calculating pagination counts for pages?
I should add that tables will only have a few thousand rows at most.
Thanks
Martin O'Shea.
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在
MyISAM
中,此查询:是即时的,因为它保存在表元数据中,因此几乎可以自由地发出此查询,并且始终会得到正确的结果。
在 InnoDB 中,此查询将逐行计数,这可能需要一些时间。
因此,如果您不需要
COUNT(*)
的精确值,您可以查询INFORMATION_SCHEMA
。In
MyISAM
, this query:is instant, since it's kept in the table metadata, so it's almost free to issue this query and it will always get the correct result.
In
InnoDB
, this query will count rows one-by-one which could take some time.So if you don't need exact value of
COUNT(*)
, you may queryINFORMATION_SCHEMA
.如果您发现
COUNT(*)
太慢,我还会考虑使用SQL_CALC_FOUND_ROWS
和SELECT FOUND_ROWS()
。I'd also consider using
SQL_CALC_FOUND_ROWS
andSELECT FOUND_ROWS()
if you findCOUNT(*)
too slow.