I have initiated a work to review the sqls of our internal software. Lot of them he problem are about sql logic, or join with table unecessary, and so on. But software has lot of sql with date, doing thinks like: [..] date >= '2009-04-01' AND date <= '2009-04-15' [..]
Redoing the SQL with fix date (date = '2009-04-01') o cost in explain always still about 200 or less. But with a period the cost is high, about 6000 or more.
Select is using Index and the date is using index too.
There is some way to use date period with less cost?