Sql-server – SET ANSI_NULLS at the database level versus setting it at the table level

sql serversql-server-2008-r2sql-standardt-sql

I have generated schema-only script for my sql server 2008 R2, here is part of it:-

USE [master]
GO
/****** Object:  Database [****]    Script Date: 03/25/2015 12:17:09 ******/
CREATE DATABASE [****] ON  PRIMARY 
( NAME = N'TMS', FILENAME = N'D:\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\****.mdf' , SIZE = 11264KB , MAXSIZE = UNLIMITED, FILEGROWTH = 1024KB )
 LOG ON 
( NAME = N'TMS_log', FILENAME = N'L:\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Data\****.ldf' , SIZE = 4672KB , MAXSIZE = 2048GB , FILEGROWTH = 10%)
GO
ALTER DATABASE [****] SET COMPATIBILITY_LEVEL = 100
GO
IF (1 = FULLTEXTSERVICEPROPERTY('IsFullTextInstalled'))
begin
EXEC [****].[dbo].[sp_fulltext_database] @action = 'enable'
end
GO
ALTER DATABASE [****] SET ANSI_NULL_DEFAULT OFF
GO
ALTER DATABASE [****] SET ANSI_NULLS OFF
GO
ALTER DATABASE [****] SET ANSI_PADDING OFF
GO
ALTER DATABASE [****] SET ANSI_WARNINGS OFF
GO
ALTER DATABASE [****] SET ARITHABORT OFF
GO
ALTER DATABASE [****] SET AUTO_CLOSE OFF
GO
ALTER DATABASE [****] SET AUTO_CREATE_STATISTICS ON
GO
ALTER DATABASE [****] SET AUTO_SHRINK OFF
GO
ALTER DATABASE [****] SET AUTO_UPDATE_STATISTICS ON
GO
ALTER DATABASE [****] SET CURSOR_CLOSE_ON_COMMIT OFF
GO
ALTER DATABASE [****] SET CURSOR_DEFAULT  GLOBAL
GO
ALTER DATABASE [****] SET CONCAT_NULL_YIELDS_NULL OFF
GO
ALTER DATABASE [****] SET NUMERIC_ROUNDABORT OFF
GO
ALTER DATABASE [****] SET QUOTED_IDENTIFIER OFF
GO
ALTER DATABASE [****] SET RECURSIVE_TRIGGERS OFF
GO
ALTER DATABASE [****] SET  DISABLE_BROKER
GO
ALTER DATABASE [****] SET AUTO_UPDATE_STATISTICS_ASYNC OFF
GO
ALTER DATABASE [****] SET DATE_CORRELATION_OPTIMIZATION OFF
GO
ALTER DATABASE [****] SET TRUSTWORTHY OFF
GO
ALTER DATABASE [****] SET ALLOW_SNAPSHOT_ISOLATION OFF
GO
ALTER DATABASE [****] SET PARAMETERIZATION SIMPLE
GO
ALTER DATABASE [****] SET READ_COMMITTED_SNAPSHOT OFF
GO
ALTER DATABASE [****] SET HONOR_BROKER_PRIORITY OFF
GO
ALTER DATABASE [****] SET  READ_WRITE
GO
ALTER DATABASE [****] SET RECOVERY FULL
GO
ALTER DATABASE [****] SET  MULTI_USER
GO
ALTER DATABASE [****] SET PAGE_VERIFY CHECKSUM
GO
ALTER DATABASE [****] SET DB_CHAINING OFF
GO
USE [****]
GO
/****** Object:  User [AD-ITSERVICES\TMSDB.user]    Script Date: 03/25/2015 12:17:09 ******/
CREATE USER [AD-ITSERVICES\test.user] FOR LOGIN [****\test.user] WITH DEFAULT_SCHEMA=[dbo]
GO
/****** Object:  Table [dbo].[TechnologyTypes]    Script Date: 03/25/2015 12:17:12 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[TechnologyTypes](
    [AssetTypeID] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](50) NOT NULL,
    [IncludedInSearch] [bit] NULL,
 CONSTRAINT [PK_AssetType] PRIMARY KEY CLUSTERED 
(
    [AssetTypeID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY],
 CONSTRAINT [IX_AssetType] UNIQUE NONCLUSTERED 
(
    [Name] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
/****** Object:  Table [dbo].[TechnologyStatus]    Script Date: 03/25/2015 12:17:12 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON

now i am confused on why i go this sentence :-

ALTER DATABASE [****] SET ANSI_NULL_DEFAULT OFF
GO
ALTER DATABASE [****] SET ANSI_NULLS OFF

but when creating any sql table i will get :-

SET ANSI_NULLS ON

so what is the final result; is ANSI_NULLS will be equal to off or on ? from my understanding the "SET ANSI_NULLS" will be OFF at the database level, unless i set it ON at the table level ? is this correct ? any why i got the ANSI_NULLs set to off at the database level ?

Best Answer

ANSI_NULL_DEFAULT { ON | OFF } :

When you dont specify ANSI_NULL_DEFAULT in CREATE TABLE or ALTER TABLE statements, this database option will determine the default value, NULL or NOT NULL for a column or CLR user-defined type.

When SET to ON, the DEFAULT value is NULL. When SET to OFF, the DEFAULT value is NOT NULL.

Connection-level settings that are set by using the SET statement override the default database-level setting for ANSI_NULL_DEFAULT. By default, ODBC and OLE DB clients issue a connection-level SET statement setting ANSI_NULL_DEFAULT to ON for the session when connecting to an instance of SQL Server.

ANSI_NULLS { ON | OFF }:

ANSI_NULL should be ON. This will be a default behavior in future versions of SQL Server.

When ANSI_NULLS is set to ON then NULLs follow the ISO compliant behavior of the Equals (=) and Not Equal To (<>) comparison operators.

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

When ANSI_NULLS is set to OFF then a comparison of NULL=NULL or NULL<>NULL returns TRUE or FALSE respectively, instead of an unknown answer NULL. It treats NULL into a value of its own.

When SET ANSI_NULLS is OFF, the Equals (=) and Not Equal To (<>) comparison operators do not follow the ISO standard. A SELECT statement that uses WHERE column_name = NULL returns the rows that have null values in column_name. A SELECT statement that uses WHERE column_name <> NULL returns the rows that have nonnull values in the column. Also, a SELECT statement that uses WHERE column_name <> XYZ_value returns all rows that are not XYZ_value and that are not NULL.

Always remember that session level setting will override database level setting for the above SET options.

Reference : SET ANSI_NULL_DFLT_ON and SET ANSI_NULLS

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