SQL Server 中的 ANSI_NULLS 标志? [英] ANSI_NULLS flag in SQL Server?

问题描述

我可以通过使用 SET ANSI_NULLS OFF 或 SET ANSI_NULLS ON

I can change the value of SET ANSI_NULLS by using SET ANSI_NULLS OFF or SET ANSI_NULLS ON

问题 #1 如何获得 当前 值?

问题 #2 设置值是否应用于查询?桌子?实例?整个数据库?

Question #2 does setting a value is applied to query? Table? Instance? Whole db?

问题 #3 如果我进入一家执行 if myNullParam <>null 的公司，我应该检查什么地方(db ? schema?查询?)告诉他们 - 这行得通，还是不行?

Question #3 If I'm entering a company which does if myNullParam <>null, what is the place which I should check (db ? schema? query ?) to tell them - this gonna work , or Not ?

谢谢.

推荐答案

1. select databasepropertyex('MyDatabaseName', 'IsAnsiNullsEnabled') 会告诉你数据库的默认值.Hitesh 的回答会告诉您当前会话的价值.
2. 数据库有默认设置，每个会话都可以覆盖数据库默认设置.
3. 会话值.但是，MSDN 文档说要使脚本按预期工作，无论 ANSI_NULLS 数据库选项或 SET ANSI_NULLS 的设置如何，请在可能包含空值的比较中使用 IS NULL 和 IS NOT NULL. 所以虽然它可能有效，但它肯定违反了最佳实践.

1. select databasepropertyex('MyDatabaseName', 'IsAnsiNullsEnabled') will tell you the database default. Hitesh's answer will tell you the value for the current session.
2. The database has a default settting, and each session can override the database default.
3. The session value. However, the MSDN documentation says For a script to work as intended, regardless of the ANSI_NULLS database option or the setting of SET ANSI_NULLS, use IS NULL and IS NOT NULL in comparisons that might contain null values. So while it may work, it's certainly against best practices.

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