Union on Dynamic (Loop) SQL Server - sql-server

Question

with the below loop script, I am creating tables for every period. What I need is that I would like to union all these multiple tables into one single table within the same script. Can anyone help me do that?
DECLARE #Interval_List as TABLE (index_1 int, Interval VARCHAR(50), Interval_2 VARCHAR(50), From_date date, To_date date)
INSERT INTO #Interval_List VALUES (1, '2021_Q3', '2021 Q3', '2021-07-01', '2021-09-30')
INSERT INTO #Interval_List VALUES (2, '2021_Q4', '2021 Q4', '2021-10-01', '2021-12-31')
INSERT INTO #Interval_List VALUES (3, '2021_H2', '2021 H2', '2021-07-01', '2021-12-31')
INSERT INTO #Interval_List VALUES (4, '2021', '2021', '2021-07-01', '2021-12-31')
DECLARE #StartDate AS DATE
DECLARE #EndDate AS DATE
DECLARE #CurrentDate AS DATE
DECLARE #index_first int
declare #index_last int
declare #interval VARCHAR(50)
declare #interval_2 VARCHAR(50)
declare #issue_table nvarchar(max)
declare #service_table nvarchar(max)
SELECT #index_first = min(index_1), #index_last = max(index_1) FROM #Interval_List
SET #CurrentDate = #StartDate
SET #issue_table = 'dbo.table1'
SET #service_table = 'dbo.table2'
WHILE (#index_first <= #index_last)
BEGIN
SELECT #StartDate = From_date, #EndDate = To_date, #interval = Interval, #interval_2 = Interval_2 FROM #Interval_List where index_1 = #index_first
IF OBJECT_ID(#issue_table) IS NULL
BEGIN
RAISERROR('Bad object!', 11, 1);
RETURN;
END
declare #query nvarchar(max);
set #query =
N'
SELECT
A.SERVICE,
A.Service_Group,
A.Portfolio,
Interval,
SUM(Metric_1_Dividend_C_New) AS Metric_1_Dividend_C_New
'
+ N'into dbo.METRIC_1_' + #interval
+
N'
FROM
(
SELECT
ISSUE_CREATION_DATE,
ISSUE_ID,
SERVICE,
SERVICE_GROUP,
PORTFOLIO,
#Interval_2 as Interval,
AVG(Metric_No_1_Dividend) AS Metric_1_Dividend_C_New
'
+ N' from ' + #issue_table +
N' where PROJECT IS NOT NULL
AND cast(FORMAT(ISSUE_CREATION_DATE, ''yyyyMMdd'') as varchar(30)) >= cast(FORMAT(#StartDate, ''yyyyMMdd'') as varchar(30))
AND cast(FORMAT(ISSUE_CREATION_DATE, ''yyyyMMdd'') as varchar(30)) <= cast(FORMAT(#EndDate, ''yyyyMMdd'') as varchar(30))
GROUP BY ISSUE_CREATION_DATE, ISSUE_ID,SERVICE,SERVICE_GROUP,PORTFOLIO
) A
GROUP BY SERVICE,Service_Group,Portfolio,Interval
'
exec sys.sp_executesql #query,
N'#StartDate date, #EndDate date, #Interval_2 VARCHAR(50)',
#StartDate, #EndDate, #Interval_2;
SET #index_first = #index_first + 1;
END
;

Answer 1

Before you continue, please make sure that you read about table partitioning and creating a view for your unions, because, intuitively the problem you describe sounds like these. If neither partitioning, nor views are good for you, then read the sections below:
How can I get tables by name
SELECT [name]
FROM sys.tables
WHERE [name] LIKE '%somepattern%'
How to generate a command:
SELECT CONCAT('INSERT INTO ', [name], '(col1, col2, col3) values(', value1, ', ', value2, ', ', value3, ')')
FROM sys.tables
WHERE [name] LIKE '%somepattern%'
How to concatenate rows
You can use STRING_AGG(yourstring, 'separator'), like:
SELECT STRING_AGG(CONCAT('INSERT INTO ', [name], '(col1, col2, col3) values(', value1, ', ', value2, ', ', value3, ')'), ' UNION ')
FROM sys.tables
WHERE [name] LIKE '%somepattern%'