[英]Check and Return rows if SQL Server table exists
我正在處理涉及SQL Server表的應用程序。 我正在寫一個查詢,其中我需要檢查一個表,如果該表存在,則需要從該表中選擇記錄,如果該表在該數據庫中不存在,則需要從另一個表中進行選擇。
我嘗試使用UDF編寫相同的內容,但未成功。 我無法使用存儲過程,因為我需要將輸出連接到另一個表。
有什么辦法嗎?
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
上面是拋出錯誤
消息444,級別16,狀態2,過程udf_site_information,第24行[批處理開始第15行]函數中包含的Select語句無法將數據返回給客戶端。
您顯然沒有收到結果。 那是因為您沒有在結果表中插入數據集:
insert into @returntable
SELECT university_id,...
添加它,它應該工作。 並更改此存在檢查,因為每個人都認為問題出在這里:)
您應該可以簡單地使用此表格
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Feeds]') AND type in (N'U'))
--abc
ELSE
-- xyz
與information_schema相同:
IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES where TABLE_NAME like 'feeds')
BEGIN
print 'exists'
END
使用OBJECT_ID()和N'U'
作為對象類型:
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
這將起作用! 您需要將查詢中的數據作為variable
返回。 您需要定義所有要用作輸出的變量。 我用我的虛擬表示例更改了您的示例。 您可以根據自己的要求使用我給您舉一個例子
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
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