如果 SQL 服务器 table 存在，则检查 Return 行

Question

我正在开发一个涉及 SQL 服务器 table 的应用程序。我正在编写一个查询，其中我需要检查 table，如果 table 存在，我需要 select 来自 table 的记录，如果 table 在我需要从另一个 table.

select 的那个数据库中不存在

我尝试用 UDF 写同样的东西，但我没有成功。我无法使用存储过程，因为我需要将输出连接到另一个 table.

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

上面是抛出的错误

Msg 444, Level 16, State 2, Procedure udf_site_information, Line 24 [Batch Start Line 15] Select statements included within a function cannot return data to a client.

Answer 1

显然，您没有收到结果。那是因为你没有在结果中插入你的数据集 table:

insert into @returntable
SELECT university_id,...

添加这个，它应该可以工作。并更改此存在性检查，因为每个人都认为问题就在那里:)

您应该能够简单地使用此表单

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

同information_schema:

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

Answer 2

使用 OBJECT_ID() 和 N'U' 作为对象类型：

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

这行得通！您需要 return 查询中的数据为 variable。您需要定义您想要的所有变量作为输出。我已经用我的虚拟表示例更改了您的示例。您可以根据您的要求使用举个例子

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

如果 SQL 服务器 table 存在，则检查 Return 行

Check and Return rows if SQL Server table exists

sql

tsql

sql-server

sql-function