Question

我正在处理一个涉及SQL Server表的应用程序。我正在写一个查询，其中我需要检查一个表，如果该表存在，则需要从该表中选择记录，如果该表在该数据库中不存在，则需要从另一个表中选择。

我尝试使用UDF编写相同的内容，但未成功。我无法使用存储过程，因为我需要将输出连接到另一个表。

有什么办法吗？

CREATE FUNCTION dbo.udf_school_information 
    (@univ_id INT)
RETURNS @returntable TABLE
(
    univ_id INT,
    school_number INT,
    school_name NVARCHAR(255),
    school_address NVARCHAR(255),
    state NVARCHAR(150),
    district NVARCHAR(100),
    start_date datetime
)
AS
BEGIN
    DECLARE @tbl_exists BIT;

    SET @tbl_exists = ISNULL((SELECT 1 FROM INFORMATION_SCHEMA.TABLES 
                              WHERE Table_Name LIKE '%School'),0)

    IF @tbl_exists = 1      
    BEGIN
        SELECT 
            university_id, school_number, school_name, 
            school_address, school_state, district, school_started_date 
        FROM 
            [dbo].[tbl_school_info] 
        WHERE 
            id = @univ_id
    END
    ELSE
    BEGIN
        ---- My condition if school_ingo table does not exists 
        ---- will be querying another table.
    END

    RETURN;
END;
GO

以上抛出错误

第444级消息，状态2，过程udf_site_information，第24行 [Batch Start Line 15]选择函数中包含的语句无法将数据返回给客户端。

Answer 1

您显然没有收到结果。那是因为您没有在结果表中插入数据集：

insert into @returntable
SELECT university_id,...

添加它，它应该可以工作。并更改此存在检查，因为每个人都认为问题出在这里：）

您应该可以简单地使用此表格

IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Feeds]') AND type in (N'U'))
  --abc
ELSE
  -- xyz

与information_schema相同：

IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES where TABLE_NAME like 'feeds')
BEGIN
 print 'exists'
END

Answer 2

将OBJECT_ID()与N'U'一起用作对象类型：

CREATE FUNCTION dbo.udf_school_information (@univ_id INT)
RETURNS @returntable TABLE
(
    univ_id INT,
    school_number INT,
    school_name NVARCHAR(255),
    school_address NVARCHAR(255),
    state NVARCHAR(150),
    district NVARCHAR(100),
    start_date datetime
)
AS
BEGIN
    DECLARE @tbl_exists BIT;

    IF OBJECT_ID(N'[dbo].[tbl_school_info]', N'U') IS NOT NULL SET @tbl_exists = 1
    ELSE SET @tbl_exists = 0;

    IF @tbl_exists = 1      
    BEGIN
       -- Statements
    ELSE
    BEGIN
        -- My condition if school_ingo table does not exists 
        -- will be querying another table.
    END
END;
GO

Answer 3

这将起作用！您需要以variable的形式返回查询中的数据。您需要定义所有要用作输出的变量。我用我的虚拟表示例更改了您的示例。您可以根据需要使用让我举一个例子

ALTER FUNCTION dbo.udf_school_information (@univ_id INT)
RETURNS @returntable TABLE
(
    univ_id INT

)
AS
BEGIN

    declare @tbl_exists bit
    Declare @Outputdata varchar(100)

    IF OBJECT_ID(N'[dbo].[tblprojectresource]', N'U') IS NOT NULL SET @tbl_exists = 1
    ELSE SET @tbl_exists = 0;

    IF @tbl_exists = 1      
    BEGIN
        select @Outputdata =ProjectResourceId from tblProjectResource Where ProjectResourceId =@univ_id
       -- Statements
    END
    ELSE
    BEGIN
        select @Outputdata =ProjectId from tblprojectmaster Where projectid =@univ_id
    END
END;
GO

检查并返回行（如果存在SQL Server表）

3 个答案: