condition if

principle of hash algorithmWhat is the principle of hash algorithm? This question is a bit difficult, not very clear, to make a metaphor: we have a lot of pigs, each weight is different, assuming that the weight distribution is relatively average

There are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article I spent a lot

There are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article I spent a lot

Share a PHP mysqli connection class complete code instance, about MYSQLI usage instance.A database class instance that joins the database in PHP in Mysqli way, the database class is organized from a PHP cms, can implement PHP connection database

Source: http://www.cnblogs.com/yunfeifei/p/3850440.htmThere are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also

Add by Zhj: The author does not specify which database, which is just an approximate general summary. For a particular database, some entries may not be applicable.Original: http://www.cnblogs.com/yunfeifei/p/3850440.htmlThere are a lot of tutorials

There are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article I spent a lot

Referenced from: http://database.51cto.com/art/201407/445934.htmThere are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but

There are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article I spent a lot

1. To optimize the query, to avoid full table scanning, first consider the where and order by the columns involved in the index.2. Avoid null-valued fields in the WHERE clause, which will cause the engine to discard full-table scans using the index,

1. To optimize the query, try toAvoid full table scan, you should first consider establishing an index on the columns involved in where and order by.2. Avoid null-valued fields in the WHERE clause, which will cause the engine to discard full-table

There are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article I spent a lot

1. Display the list of databasesshow databases; # View all current databasesShow Databases \g #以行的方式显示2. On the command line, execute the SQL statementMysql-e ' show databases '-uroot-p123456mysqlshow-uroot-p123456 # not used, just remember the one

1. To avoid full-table scanning, first consider establishing an index on the columns involved in the Where and order by.2. Avoid null-valued fields in the WHERE clause, which will cause the engine to discard full-table scans using the index, such as:

When writing query statements, be sure to pay attention to performance issues.Here are some of the methods I collected to raise the performance, not the whole point of looking at a lot of advice.　　1. To optimize the query, it is important to avoid

Original address: http://blog.csdn.net/u011721927/article/details/39228001First, syntax and rationale for update statements1.GrammarSingle tableUPDATEtable name set column name = new value WHERE column name = value such as:

There are many scenarios for SQL optimization on the web, but many are disorganized. Recently leisure time to tidy up a bit, convenient for everyone after the inspection, if found that there are any problems and not all, welcome to the following

Cloud drizzlingThere are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article

1, problem descriptionHow does a SQL work in a database? I believe a lot of people will be interested in this problem. Of course, to fully describe a SQL in the database life cycle, this is a very big problem, covering the SQL lexical parsing,

There are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement.This article I spent a lot