SQLite, MySQL, PHP: Ternary operator (IF() statement) in MySQL and SQLite SQLite的，MySQL和PHP：三元运算符（中频（）语句）在MySQL和SQLite

Posted on 03.发布03。 Feb, 2010 by Dragos in Coding , MySQL , PHP , SQLite 2008年2月，2010年在编码，MySQL的，PHP的，SQLite的德拉戈什

While working on a proxy checker tool for one of my projects, I was struggling on how to execute a conditional query on my SQLite database to update a column only if its value is greater than 0 (it would be pointless in my case to let the script update the column with negative values).而在代理检查工具的工作为我的项目之一，我很难就如何执行我的SQLite数据库有条件的查询来更新列仅当它的值大于0（这将是对我来说，毫无意义，让脚本更新负值的列）。

In Mysql one would do like this (we use the ternary operator IF(to_check_expression>0,expression1,expression2) ):在MySQL的人会不喜欢这样（我们使用IF（to_check_expression“0，expression1的，expression2的））的三元运算符：

update table_name set column_name=IF((column_name-1)>0,(column_name-1),0)

However, in SQLite this method will not work.然而，在SQLite的这种方法是行不通的。 Instead I had to use the case when (condition) then expression1 else expression2 end method.相反，我不得不使用的情况时（条件），那么expression1的其他expression2的结束方式。

The above query in MySQL can be rewritten like this in SQLite:在MySQL上述查询可以改写这样在SQLite：

update table_name set column_name=case when (column_name-1)>0 then (column_name-1) else 0 end

That's it.就是这样。 I hope it helps someone!我希望它可以帮助别人！