SQL操作應(yīng)用——在屬性上進(jìn)行計(jì)算不能命中索引

select * from order where YEAR(date) < = ‘2017’

即使date上建立了索引，也會全表掃描，可優(yōu)化為值計(jì)算：

select * from order where date < = CURDATE()
或者：
select * from order where date < = ‘2017-01-01’