how to get table from first table when data is not there in second table - sql

Question

i have requirement where i need to show data of both tables when both the ID's are same.when id is present in first table and not there in second table i need to show data from first table
CREATE TABLE [dbo].[TEST](
[ID] [int] NULL,
[Name] [varchar](10) NULL,
[Status] [char](1) NULL,
[CreatedDate] [datetime] NULL
) ON [PRIMARY]
GO
CREATE TABLE [dbo].[Test_History](
[ID] [int] NULL,
[Name] [varchar](10) NULL,
[Status] [char](1) NULL,
[CreatedDate] [datetime] NULL
) ON [PRIMARY]
GO
/****** Object: Table [dbo].[Test_History] Script Date: 06/19/2015 19:01:49 ******/
INSERT [dbo].[Test_History] ([ID], [Name], [Status], [CreatedDate]) VALUES (1, N'Mohan', N'A', CAST(0x0000A4BC01347E88 AS DateTime))
INSERT [dbo].[Test_History] ([ID], [Name], [Status], [CreatedDate]) VALUES (1, N'Mohan', N'I', CAST(0x0000A4BC0134A390 AS DateTime))
INSERT [dbo].[Test_History] ([ID], [Name], [Status], [CreatedDate]) VALUES (2, N'Rohan', N'A', CAST(0x0000A4BC01391FCC AS DateTime))
/****** Object: Table [dbo].[TEST] Script Date: 06/19/2015 19:01:49 ******/
INSERT [dbo].[TEST] ([ID], [Name], [Status], [CreatedDate]) VALUES (2, N'Rohan', N'I', CAST(0x0000A4BC0138D584 AS DateTime))
INSERT [dbo].[TEST] ([ID], [Name], [Status], [CreatedDate]) VALUES (1, N'Mohan', N'A', CAST(0x0000A4BC013072DC AS DateTime))
INSERT [dbo].[TEST] ([ID], [Name], [Status], [CreatedDate]) VALUES (3, N'Raj', N'A', CAST(0x0000A4BC0138DED7 AS DateTime))
INSERT [dbo].[TEST] ([ID], [Name], [Status], [CreatedDate]) VALUES (4, N'Krishna', N'A', CAST(0x0000A4BC0138EE31 AS DateTime))
so far i have tried my query to achieve the result
select T.ID,COALESCE(T.ID,TT.ID),T.Name,COALESCE(T.Name,TT.Name),T.status,COALESCE(T.status,TT.status)
from Test T LEFT JOIN (Select TOP 1 ID,MIN(Name)name,Status from Test_History
GROUP BY ID,status
)TT
ON T.ID = TT.ID
where T.ID = 3
Id = 1 and 2 present show i will get data from both tables
Id = 3 and 4 not present in the table
so using coalesce i will get the data
from first table and show in 2nd table column also
but is there any other way like both tables are same structure
i'm thinking of
Declare #tablename varchar(10)
IF EXISTS (SELECT 1 from TESt where id = #id)
IF COunt there in both tables
SET #tablename = Test
ELSE
SET #tablename = Test_history
select * from #tablename where id = #ID
can i get any solution like this

Answer 1

You can use EXCEPT.
Here is an example:
SELECT a,b
FROM (
VALUES (1, 2), (3, 4), (5, 6), (7, 8), (9, 10)
) AS MyTable(a, b)
EXCEPT
SELECT a,b
FROM (
VALUES (1, 2), (7, 8), (9, 10)
) AS MyTable(a, b);
This will return all rows of the upper statement, which are not in the second statement.

Answer 2

First: Thanks for the excellent setup for the data related to the question!
If your real question was if table variables can be used as described in your question, the answer is no; or more accurately that its not worth it.
Not recommended:
declare #TableName TABLE (
[ID] [int] NULL,
[Name] [varchar](10) NULL,
[Status] [char](1) NULL,
[CreatedDate] [datetime] NULL)
IF EXISTS (SELECT 1 from TESt where id = #id)
INSERT INTO #TableName SELECT * FROM dbo.TEST WHERE ID = #ID
ELSE INSERT INTO #TableName SELECT * FROM dbo.[Test_History] WHERE ID = #ID
select * from #tablename where id = #ID
Here's the solution I prefer:
DECLARE #ID INT = 3;
SELECT * FROM [dbo].[TEST] ss WHERE ss.id = #id
UNION ALL SELECT * FROM [dbo].[Test_History] th WHERE th.id = #id
and not exists ( SELECT * FROM [dbo].[TEST] ss WHERE ss.id = #id);
UNION ALL performs surprisingly well - don't forget the ALL keyword, and I am assuming that ID is a PK or AK.

Answer 3

If I'm understanding correctly and you want to display all records that match between the two tables and only records from first table when the id does not exist in the second in the same result set, then all you need is a simple left join:
SELECT *
FROM dbo.test t
LEFT OUTER JOIN Test_History th
ON t.id = th.id
WHERE t.id = #id