我收到“错误消息 512，级别 16，状态 1，第 1 行子查询返回超过 1 个值”

Question

在尝试确定特定集群上高可用性数据库的状态时，我收到了标题的错误消息。

消息 512，第 16 级，状态 1，第 1 行
子查询返回超过 1 个值。当子查询跟随 =、!=、、>= 或子查询用作表达式时，这是不允许的

这是我的代码的一部分。我需要能够利用两个 select 语句的结果，然后在两者都满足时分配 @HadrRole。

IF ((SELECT ars.role
     FROM sys.dm_hadr_availability_replica_states ars
     INNER JOIN sys.databases dbs
     ON ars.replica_id = dbs.replica_id
     WHERE dbs.name = @DatabaseName) = 2 AND (SELECT secondary_role_allow_connections_desc
     FROM sys.availability_replicas) ='ALL')
SET @HadrRole = 3

Answer 1

尝试使用EXISTS子查询：

IF EXISTS 
    (
        SELECT *
        FROM sys.dm_hadr_availability_replica_states ars
        INNER JOIN sys.databases dbs
        ON ars.replica_id = dbs.replica_id
        WHERE dbs.name = @DatabaseName AND ars.role = 2
    ) AND 
    EXISTS 
    (
        SELECT  *
        FROM    sys.availability_replicas
        WHERE   secondary_role_allow_connections_desc = 'ALL'
    )
SET @HadrRole = 3

注意：您可以这样使用SET 语句：

SET @HadrRole = 
    CASE 
    WHEN EXISTS 
        (
            SELECT *
            FROM sys.dm_hadr_availability_replica_states ars
            INNER JOIN sys.databases dbs
            ON ars.replica_id = dbs.replica_id
            WHERE dbs.name = @DatabaseName AND ars.role = 2
        ) 
        AND EXISTS 
        (
            SELECT  *
            FROM    sys.availability_replicas
            WHERE   secondary_role_allow_connections_desc = 'ALL'
        )
    THEN 3 
    ELSE @HadrRole 
    END

Answer 2

我用它来确定集群中每台服务器上的高可用性数据库是主数据库、辅助数据库还是只读辅助数据库。我将使用它来修改我的 SQL 代理作业，以便它们在集群中的正确服务器上运行（根据作业只读辅助或主服务器。感谢您的回复！我希望这对其他人有所帮助。

USE [msdb]
GO

/****** Object:  UserDefinedFunction [dbo].[RG_fn_HA_isPrimaryReplica_isSecondayReadable]    Script Date: 1/27/2014 4:31:39 PM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO
IF object_id(N'RG_fn_HA_isPrimaryReplica_isSecondayReadable', 'FN') IS NOT NULL
    DROP FUNCTION RG_fn_HA_isPrimaryReplica_isSecondayReadable
    GO
CREATE FUNCTION [dbo].[RG_fn_HA_isPrimaryReplica_isSecondayReadable] (@DatabaseName SYSNAME)
RETURNS TINYINT
WITH EXECUTE AS CALLER
AS
/********************************************************************
  File Name:    RG_fn_HA_isPrimaryReplica_isSecondayReadable.sql
  Applies to:   SQL Server 2012
  Purpose:      To return either 0, 1, or 2 based on whether this
                @DatabaseName is a primary or secondary replica.
  Parameters:   @DatabaseName - The name of the database to check.
  Returns:      0 = Resolving
                1 = Primary
                2 = Secondary 
                3 = Readable Secondary
  Author:       Matthew Joyce
  Version:      1.0.0 - 01/28/2014
********************************************************************/
BEGIN
    DECLARE @HadrRole TINYINT
    -- Return role status from sys.dm_hadr_availability_replica_states
    IF (SELECT ars.role
        FROM sys.dm_hadr_availability_replica_states ars
        INNER JOIN sys.databases dbs
        ON ars.replica_id = dbs.replica_id
        WHERE dbs.name = @DatabaseName) = 1
        SET @HadrRole = 1
ELSE
    -- @DatabaseName exists but does not belong to an AG so return 1
    --  IF @HadrRole IS NULL
        --SET @HadrRole = 1
--ELSE 
    --Return 2 if secondary but not readable
     IF (SELECT ars.role
        FROM sys.dm_hadr_availability_replica_states ars
        INNER JOIN sys.databases dbs
        ON ars.replica_id = dbs.replica_id
        WHERE dbs.name = @DatabaseName) = 2 AND (SELECT secondary_role_allow_connections_desc
        FROM sys.availability_replicas
        where replica_server_name =(select @@ServerName)) <>'ALL'
SET @HadrRole = 2
ELSE 
     IF (SELECT ars.role
        FROM sys.dm_hadr_availability_replica_states ars
        INNER JOIN sys.databases dbs
        ON ars.replica_id = dbs.replica_id
        WHERE dbs.name = @DatabaseName) = 2 AND (SELECT secondary_role_allow_connections_desc
        FROM sys.availability_replicas
        where replica_server_name =(select @@ServerName)) ='ALL'
SET @HadrRole = 3
        RETURN @HadrRole;
END;
GO