小编h.c*_*tes的帖子

我在一些示例数据库中看到,人们喜欢将字段大小舍入为基数2的倍数(例如varchar(32)或varchar(64)),就像它给予它们更好的性能或空间利用率一样.这种做法有什么好处吗？或者这只是人们迂腐？

谢谢你的期待

$ timeposted ="晚上7:10";

此值目前是加拿大时间(魁北克省).我正试图找到一种方法将其转换为法国的时间.我怎样才能做到这一点 ？

我有一个带有多个连接的select语句,每个连接都有一个名为'created_on'的列名,是否有一种方法可以使查询的where部分检查所有3个表？这是我做的实际查询

SELECT *
FROM household_address
JOIN catchment_area ON catchment_area.household_id = household_address.household_id
JOIN bhw ON catchment_area.bhw_id = bhw.user_username
JOIN master_list ON master_list.person_id = catchment_area.person_id
JOIN house_visits ON house_visits.household_id = household_address.household_id
WHERE catchment_area.household_id IN (
  SELECT household_address.household_id
  FROM demo.household_address
  JOIN catchment_area ON catchment_area.household_id = household_address.household_id
  JOIN previous_cases ON catchment_area.person_id = previous_cases.person_id
  JOIN active_cases ON catchment_area.person_id = active_cases.person_id
  JOIN ls_report ON ls_report.ls_household = household_address.household_name
  WHERE DATE(created_on) BETWEEN '2014-03-01' AND '2014-03-31' 
)

我正在谈论的连接是子查询中的连接.