sql-server – `SET ANSI_NULLS OFF`做什么？

解决方法

The SQL-92 standard requires that an equals (=) or not equal to (<>) comparison against a null value evaluates to FALSE.

When SET ANSI_NULLS is ON,a SELECT statement using WHERE column_name = NULL returns zero rows even if there are null values in column_name. A SELECT statement using WHERE column_name <> NULL returns zero rows even if there are non-null values in column_name.

When SET ANSI_NULLS is OFF,the Equals (=) and Not Equal To (<>) comparison operators do not follow the SQL-92 standard. A SELECT statement using WHERE column_name = NULL returns the rows with null values in column_name. A SELECT statement using WHERE column_name <> NULL returns the rows with non-null values in the column. In addition,a SELECT statement using WHERE column_name <> XYZ_value returns all rows that are not XYZ_value and that are not NULL.

（编辑：李大同）

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