Database

1. Use a different name for each table variable or delete the content and reuse the existing variable
2. Why are you scared to use Delete!
3. Table variables are limited in scope to the current procedure.

SELECT DATE(attendance_date_time) AS attendance_date, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(TIME(attendance_date_time)), ',', 1), ',', -1) AS F1,
IF(LENGTH(GROUP_CONCAT(TIME(attendance_date_time))) - LENGTH(REPLACE(GROUP_CONCAT(TIME(attendance_date_time)), ',', '')) > 1,
SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(TIME(attendance_date_time)), ',', 2), ',', -1) ,NULL) AS F2,
SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(TIME(attendance_date_time)), ',', 3), ',', -1) AS F3,
SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(TIME(attendance_date_time)), ',', 4), ',', -1) AS F4
FROM employee_attendance
GROUP BY DATE(attendance_date_time);

Insert into TableC (TableAId, AnotherTableAId, TableAName, AnotherTableAName)
SELECT TableAId, AnotherTableAId, TableAName, AnotherTableAName FROM TableB b
INNER JOIN TableA a2 ON a2.Name = b. AnotherTableAName
UNION
Insert into TableC (TableAId, AnotherTableAId, TableAName, AnotherTableAName)
SELECT TableAId, AnotherTableAId, TableAName, AnotherTableAName FROM TableB b
INNER JOIN TableA a ON a.Name = b. TableAName

--Insert into #TableC (TableAId, AnotherTableAId, TableAName, AnotherTableAName)
SELECT TableAId, AnotherTableAId, TableAName, AnotherTableAName FROM #TableB b
INNER JOIN #TableA a ON a.Name = b.TableAName  OR a.Name = b.AnotherTableAName

DECLARE @DOB DATETIME = GETDATE()
DECLARE @ODate DATE
DECLARE @OHour INT = 8
DECLARE @OMin INT = 23
DECLARE @OpenDT DATETIME

SELECT @ODate = CONVERT(DATE,@DOB)
SET @OpenDT = @ODate
SELECT @OpenDT = DATEADD(HOUR,@OHour,@OpenDT)
SELECT @OpenDT = DATEADD(MINUTE,@OMin,@OpenDT)

PRINT @OpenDT

DECLARE @ODate DATE
DECLARE @OHour INT = 8
DECLARE @OMin INT = 23
DECLARE @OpenDT DATETIME
declare @DOB DATE = getdate()  --Or whatever date drom the database
SELECT @OpenDT = @DOB

SELECT @OpenDT = DATEADD(MINUTE,(@OHour * 60) + @OMin, @OpenDT)

PRINT @OpenDT

DECLARE @TabAId int;
INSERT INTO TabA (CurrentDate) VALUES (GetUtcDate());
SET @TabAId = Scope_Identity();

INSERT INTO TabC (Col1, Col2, TabAId)
SELECT Col1, Col2, @TabAId FROM TabB;

DECLARE @MyTableVar table (DocumentListId int, [Name] varchar(max), [Description] varchar(max));
INSERT INTO dbo.DocumentList (CreatedDate,CreatedBy,ModifiedDate,ModifiedBy)
  OUTPUT INSERTED.DocumentListId, 
         htge.[Name], 
         htge.[Description]
  INTO @MyTableVar
SELECT  GETDATE() ,CURRENT_USER,GETDATE(),CURRENT_USER, htge.[Name], htge.[Description]
FROM    OPENROWSET('SQLNCLI', 'Server=xxx;UID=xx;PWD=xxx',
        'SELECT * FROM WEB_WebAdmin.dbo.HealthTopicGroup where HealthTopicGroupId < 45') as htge;

SELECT * frOM @MyTableVar