对于单列索引,尽量选择针对当前query过滤性更好的索引 在选择组合索引的时候,当前query中过滤性最好的字段在索引字段顺序中,位置越靠前越好。 在选择组合索引的时候,尽量选择能够包含当前query中的where子句中更多字段的索引。 在选择组合索引的时候,如果某个字段可能出现范围查询时,尽量把这个字段放在索引次序的最后面。
Query OK, 3 rows affected (0.00 sec) 1. 2. 11.删除数据 mysql>delete from table01swheresfield01=3; Query OK, 1 row affected (0.00 sec) 1. 2. 12.导入数据库表 (1)创建.sql文件 (2)先产生一个库如auction.c:/mysql/bin>mysqladmin -u root -p creat auction,会提示输入密码,然后成功创建。
Re: Date/Time Query Mark Snyder April 09, 2009 09:14AM Re: Date/Time Query A Ford April 09, 2009 11:14AM Re: Date/Time Query Rick James April 11, 2009 10:32PM Re: Date/Time Query A Ford April 13, 2009 01:19PM Sorry, you can't reply to this topic. It has been closed....
we will get no result! This is because the query is looking only for dates with no time portion. Tip:To keep your queries simple and easy to maintain, do not use time-components in your dates, unless you have to! Exercise? Which of the following is the correct format for theDATEdata...
NO_ZERO_IN_DATE 只设置NO_ZERO_IN_DATE, 异常数据会产生Warning,但是数据能写入 -- 设置NO_ZERO_IN_DATE, 日期、月份为0的数据会触发warning mysql> set sql_mode='NO_ZERO_IN_DATE'; Query OK, 0 rows affected, 1 warning (0.01 sec)
只设置NO_ZERO_IN_DATE, 异常数据会产生Warning,但是数据能写入 -- 设置NO_ZERO_IN_DATE, 日期、月份为0的数据会触发warning mysql> set sql_mode='NO_ZERO_IN_DATE'; Query OK, 0 rows affected, 1 warning (0.01 sec) mysql> insert into t_date values('2022-01-00'); Query OK, 1 row affecte...
in 操作也可以用于子查询动态的获取列表信息: inner_qs = Blog.objects.filter(name__contains='hunter') Entry.objects.filter(blog__in=inner_qs) 注意,以上的QuerySet 只在第二步的时候会去查询数据库,其SQL类似于: select * from blog_entry where blog_id in (select id from blog_blog where name ...
mysql> CREATE TABLE sales(ID INT,ProductName VARCHAR(255),CustomerName VARCHAR(255),DispatchDate date,DispatchTime time,Price INT,Location VARCHAR(255));Query OK, 0 rows affected (2.22 sec)现在，我们将使用 INSERT 语句在Sales表中插入 5 条记录：insert into sales values (1, 'Key-Board', '...
mysql> SELECT something FROM tbl_name -> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col; The query also selects rows with dates that lie in the future. Functions that expect date values usually accept datetime values and ignore the time part. Functions that expect time values usu...
Date Query Jay Balan October 06, 2006 02:00PM Re: Date Query Bob Field October 06, 2006 06:44PM Re: Date Query Jay Balan October 10, 2006 09:37AM Re: Date Query Bob Field October 10, 2006 09:58AM Re: Date Query Jay Balan ...