null vs blank

When a field in the database is set to Null, the mobile phone will return Null by default. if I want the mobile phone to return Null, I have to make a judgment. 1. if I want to leave the returned result blank on the mobile phone, I will not make any

---DQL: Data query statementsThe---Select statement must contain at least two words, namely the Select and from words.---the SELECT clause to specify the field to query.---the table that the FROM clause uses to customize the data source. The--select

Today, I went to the topic bugs & workarounds in codeproject and saw some bugs in Dev for "Quick Start". I am sympathetic to: (and Quick Start workaround, admire :) Although I have not met most of them, I would like to brief you on repro and

https://www.zhihu.com/question/21418449Mort | Zsh vs. Bash: Incomplete contrast resolution (1) 2014-10-07BdpqlxzWhat's the difference between zsh and bash?A lot of people have written about "why zsh is better than bash", "Why zsh is better than

ASP. net mvc V2 Preview 1 official homepage: http://aspnet.codeplex.com/can be downloaded here The following is a repost from a netizen, which is detailed: The preview version is in. NET 3.5 SP1 and VS 2008, which can work with ASP. net mvc 1.0 is

VS. NET (C #) Database Interface: SqlCommand object SqlParameter defends against "SQL injection" attacks, vs.net When updating a able or DataSet, if SqlParameter is not used, the entered SQL statement is ambiguous. If a string contains single

Small knowledge A hash table, an in-memory object, uses a fast hashtable when the dictionary tables, record primary keys and content. @, encountered escape character, not escaped, direct output, that is. The escape character is a backslash/all

// ================================================ ====================================// Title:// C ++ vs C # (6): entry function, which is used to change the parameter value.// Author:// Norains// Date:// Wednesday 16-January-2011// Environment://

// ================================================ ====================================// TITLE:// C ++ vs c # (6): entry function, which is used to change the parameter value.// AUTHOR:// Norains// DATE:// Wednesday 16-January-2011// Environment://

{Code ...} this method is used to obtain the corresponding val value for the Mark $ key. I return $ v at the end of the method, and then I assign the return result to a value $ va, this value is always blank, but I have a value when printing $ v at