大约有 7,000 项符合查询结果（耗时：0.0246秒） [XML]
Best practices for SQL varchar column length [closed]
... table's varchar column. But I could not find any reference for that.
For MySQL the manual says "In most cases, ALTER TABLE makes a temporary copy of the original table". And my own tests confirm that: running an ALTER TABLE on a table with 1.2 million rows (the same as in my test with Postgres) to...
常用Sql - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
常用Sqlmysql：drop table if exists tablename;不能写成drop table tablename if exists tablename;mysql：建立索引SqlCREATE TABLE t...mysql：drop table if exists tablename;
不能写成
drop table tablename if exists tablename;
mysql：建立索引Sql
CREATE TABLE tablename (
`ID...
PHP的函数前加上“@”的作用 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...供的错误信息屏蔽的专用符号。比如在一个函数前使用@@mysql_query 不会出现Warning，而原来mysql_query 在遇到错误时会在页面上访提示Warning。@是PHP提供的错误信息屏蔽的专用符号。
比如在一个函数前使用@
@mysql_query 不会出现Warning...
Curses library not found. Please install appropriate package - 更多...
Curses library not found. Please install appropriate packageCentOS安装MySql报错：-- Could NOT find Curses (missing: CURSES_LIBRARY CURSES_INCLUDE_PATH)CMake Error at cmake readli...CentOS安装MySql报错：
-- Could NOT find Curses (missing: CURSES_LIBRARY CURSES_INCLUDE_PATH)
CMake Err...
count(*) vs count(column-name) - which is more correct? [duplicate]
...
there is a performance difference (at least in MySQL) as well (see my answer).
– nickf
Jun 9 '10 at 7:51
1
...
LIMIT 10..20 in SQL Server
... not part of standard SQL. It's supported as a vendor extension to SQL by MySQL, PostgreSQL, and SQLite.
Other brands of database may have similar features (e.g. TOP in Microsoft SQL Server), but these don't always work identically.
It's hard to use TOP in Microsoft SQL Server to mimic the LIMI...
Count the number of occurrences of a string in a VARCHAR field?
...test 0
test4 valuevaluevaluevaluevalue 5
I don't have MySQL install, but goggled to find the Equivalent of LEN is LENGTH while REPLACE is same.
So the equivalent query in MySql should be
SELECT TITLE,DESCRIPTION, (LENGTH(DESCRIPTION) - LENGTH(REPLACE(DESCRIPTION, 'value', ''))...
UTF-8: General? Bin? Unicode?
...only one-to-one comparisons between characters.
Quoted from:
http://dev.mysql.com/doc/refman/5.0/en/charset-unicode-sets.html
For more detailed explanation, please read the following post from MySQL forums:
http://forums.mysql.com/read.php?103,187048,188748
As for utf8_bin:
Both utf8_general_ci...
In MySQL queries, why use join instead of where?
... Performance Perspective:
Where supported (Oracle 9i+, PostgreSQL 7.2+, MySQL 3.23+, SQL Server 2000+), there is no performance benefit to using either syntax over the other. The optimizer sees them as the same query. But more complex queries can benefit from using ANSI-92 syntax:
Ability to ...
一个科技公司只是碰巧卖起了披萨？ - 资讯 - 清泛网 - 专注C/C++及内核技术
...执行送餐，最高时速可达每小时12.5公里。顾客可以通过密码解锁，打开DRU自助取餐。
2016年4月，达美乐又推出新App一键下单——“一键”的意思是：“点开App，而不需任何其他操作”，10秒内倒计时确认非误操作，就会完成下...