I have a mysql table on innodb with 4.5ish million rows.
Why is there a HUGE time difference between these (seemingly to me) almost identical select statement?
url
is varchar(200)
select * from table where url = 12345; take 2.715 seconds
select * from table where url = "12345"; takes 0.000 seconds
Thanks in advance
I think you'll find the following information enlightening.
https://bugs.mysql.com/bug.php?id=32308
http://dev.mysql.com/doc/refman/5.0/en/type-conversion.html
Notably, the documentation clearly states (emphasis mine):
For comparisons of a string column with a number, MySQL cannot use an index on the column to look up the value quickly . If str_col is an indexed string column, the index cannot be used when performing the lookup in the following statement:
SELECT * FROM tbl_name WHERE str_col=1;
The reason for this is that there are many different strings that may convert to the value
1
, such as'1'
,' 1'
, or'1a'
.
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