QUOTED_IDENTIFIER 选项对 index 的影响

在修改或创建Index时，有时会收到一些Error Message，指明Set options设置错误，最常见的选项是：SET QUOTED_IDENTIFIER 选项

1. 当创建或修改的index包含computed columns ，必须 SET QUOTED_IDENTIFIER=ON；
2. 当创建或修改Indexed View上的Index时，必须 SET QUOTED_IDENTIFIER=ON；
3. 当创建或修改filtered index时，必须 SET QUOTED_IDENTIFIER=ON；

一，Case

早上，发现用于处理Index fragmentation的Job跑失败了，查看job history，发现以下Error Message：

ALTER INDEX failed because the following SET options have incorrect settings: 'QUOTED_IDENTIFIER'. Verify that SET options are correct for use with indexed views and/or indexes on computed columns and/or filtered indexes and/or query notifications and/or XML data type methods and/or spatial index operations. [SQLSTATE 42000] (Error 1934).  The step failed.

错误原因是：没有 SET QUOTED_IDENTIFIER =ON。

MSDN的解释是：

• SET QUOTED_IDENTIFIER must be ON when you are creating or changing indexes on computed columns or indexed views. If SET QUOTED_IDENTIFIER is OFF, CREATE, UPDATE, INSERT, and DELETE statements on tables with indexes on computed columns or indexed views will fail.
• SET QUOTED_IDENTIFIER must be ON when you are creating a filtered index.
• SET QUOTED_IDENTIFIER must be ON when you invoke XML data type methods.

二，SET QUOTED_IDENTIFIER 选项的作用，将双引号作为定界符，SQL Server默认的定界符是：[]

When SET QUOTED_IDENTIFIER is ON, identifiers can be delimited by double quotation marks, and literals must be delimited by single quotation marks.

When SET QUOTED_IDENTIFIER is OFF, identifiers cannot be quoted and must follow all Transact-SQL rules for identifiers. Literals can be delimited by either single or double quotation marks.

当设置QUOTED_IDENTIFIER时，使用双引号的字符串都会被解释为一个 Object 的标识，因此，如果要标识一个字符串，必须使用单引号。

When SET QUOTED_IDENTIFIER is ON (default), all strings delimited by double quotation marks are interpreted as object identifiers. Therefore, quoted identifiers do not have to follow the Transact-SQL rules for identifiers. They can be reserved keywords and can include characters not generally allowed in Transact-SQL identifiers. Double quotation marks cannot be used to delimit literal string expressions; single quotation marks must be used to enclose literal strings. If a single quotation mark (') is part of the literal string, it can be represented by two single quotation marks ("). SET QUOTED_IDENTIFIER must be ON when reserved keywords are used for object names in the database.

When SET QUOTED_IDENTIFIER is OFF, literal strings in expressions can be delimited by single or double quotation marks. If a literal string is delimited by double quotation marks, the string can contain embedded single quotation marks, such as apostrophes.

1，delimiting identifiers

当 SET QUOTED_IDENTIFIER=ON时，SQL Server将双引号作为界定符，功能和默认定界符 中括号 [] 相同。

而中括号作为定界符是不受Quoted_Identifier 选项设置的影响的，始终可以作为定界符使用。

Using brackets, [ and ], to delimit identifiers is not affected by the QUOTED_IDENTIFIER setting.

select是关键字，不能用于用户定义的object，除非使用定界符。当SET QUOTED_IDENTIFIER ON 时，可以使用双引号“select”，这样select关键字就能作为Table Name，作用和[select]相同。

SET QUOTED_IDENTIFIER OFF
GO
-- An attempt to create a table with a reserved keyword as a name
-- should fail.
CREATE TABLE "select" ("identity" INT IDENTITY NOT NULL, "order" INT NOT NULL);
GO

SET QUOTED_IDENTIFIER ON;
GO

-- Will succeed.
CREATE TABLE "select" ("identity" INT IDENTITY NOT NULL, "order" INT NOT NULL);
GO

SELECT "identity","order" 
FROM "select"
ORDER BY "order";
GO

DROP TABLE "SELECT";
GO

SET QUOTED_IDENTIFIER OFF;
GO

2，当 SET QUOTED_IDENTIFIER=ON时，字符串必须使用单引号

当SET QUOTED_IDENTIFIER=OFF时，字符串可以使用使用单引号，也可以使用双引号

SET QUOTED_IDENTIFIER ON;
GO
--success
DECLARE @var varchar(10)
set @var='abc'
select @var
GO

--failure
DECLARE @var varchar(10)
set @var="abc"
select @var
GO


SET QUOTED_IDENTIFIER OFF;
GO
--success
DECLARE @var varchar(10)
set @var='abc'
select @var
GO

--success
DECLARE @var varchar(10)
set @var="abc"
select @var
GO

报错信息：非法的Column Name，很奇怪的错误信息。当设置QUOTED_IDENTIFIER时，双引号标识的字符串会被解释为一个 Object 的标识。
Invalid column name 'abc'.

二, 从 sys.databases 中查看到Quoted_Identifier 选项的设置

select db.name,db.database_id,  db.is_quoted_identifier_on
from sys.databases db

三, Scope

Set QUOTED_IDENTIFIER 语句只会影响当前的Session，并且是在Parse 时设置的。

SET QUOTED_IDENTIFIER is set at parse time. Setting at parse time means that if the SET statement is present in the batch or stored procedure, it takes effect, regardless of whether code execution actually reaches that point; and the SET statement takes effect before any statements are executed. When multiple conflicting SET statements are present in the batch, the last setting parsed is used.

四，和 Set ArithAbort 搭配使用

在使用Sql Server Agent删除数据的时候，SQL Server抛出Error：

DELETE failed because the following SET options have incorrect settings: 'QUOTED_IDENTIFIER'. Verify that SET options are correct for use with indexed views and/or indexes on computed columns and/or filtered indexes and/or query notifications and/or XML data type methods and/or spatial index operations. [SQLSTATE 42000] (Error 1934).  The step failed.

解决方案是：在 delete 语句之前加入两个set options

SET ARITHABORT ON
SET QUOTED_IDENTIFIER ON

在创建或修改Index时，记得在语句前面加上：SET QUOTED_IDENTIFIER ON 和 SET ARITHABORT ON。

参考文档：

SET QUOTED_IDENTIFIER (Transact-SQL)