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TRUNCATE and INSERT INTO SQL table DYNAMICALLY based on columns in SQL table.

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Last Modified: 2018-12-06
Hello Experts,

I have a SQL table. See attached copy.

I have multiple companies in companyname column with each corresponding Select statements from each dbo. files table. Each company have exactly the same column fields. I want to insert each company "SelectFromTable" column into table in "InsertIntoTable" column dynamically. But before inserting into table, I want to delete the table first dynamically.

This is what I want to accomplish with the query:

Select "TrucateTable" , "InsertIntoTable" from dbo.DynamicTable

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Can this be possible?

Thank you again for all your help.
TRUNCATEandINSERTtableDYNAMICALLY.xlsx
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Author

Commented:
Please help. Thank you.
Doug BishopDatabase Developer

Commented:
Try this:
DECLARE @SQL VARCHAR(MAX);
DECLARE @SelectFromTable VARCHAR(128) = 'AAAfiles';
DECLARE @InsertIntoTable VARCHAR(128) = 'BalanceAmtTable';
SET @SQL = 'TRUNCATE TABLE dbo.' + @InsertIntoTable +'; INSERT INTO dbo.' + @InsertIntoTable + ' (Amt, BalanceAmt, Reasons, DateDue) SELECT Amt, BalanceAmt, Reasons, DateDue FROM dbo.' + @SelectFromTable + ' WHERE BalanceAmt >= Dateadd(Month, Datediff(Month, 0, DATEADD(m, -3, current_timestamp)), 0)  AND Amt = 0;'
EXECUTE (@SQL);

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If you put it into a procedure, you can pass @SelectFromTable and @InsertIntoTable as parameters and remove them from the code above.
Doug BishopDatabase Developer

Commented:
Are you wanting to pull the names from another table (e.g. DynamicTable) or just supply the from and to table names?
Zakaria AcharkiAnalyst Developer
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Distinguished Expert 2018

Commented:
I'm not sure if that what you mean but you could truncate the table for the first time :

TRUNCATE TABLE dbo.BalanceAmtTable

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Then perform an insert query from table to table multiple time as much as companies you've :

INSERT INTO dbo.BalanceAmtTable(Amt,BalanceAmt,Reasons,DateDue)
SELECT  Amt, BalanceAmt, Reasons, DateDue 
	FROM dbo.AAAfiles 
	WHERE BalanceAmt >= Dateadd(Month, Datediff(Month, 0, DATEADD(m, -3, current_timestamp)), 0)  AND Amt = 0

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The insert query could be saved as a PROCEDURE and then pass the table name dbo.XXXfiles as parameter to it.

Author

Commented:
@Doug Bishop:

I will test your SQL query and execute my Stored Procedure and I will let you know as soon as I finish.

Are you wanting to pull the names from another table (e.g. DynamicTable) or just supply the from and to table names?

I want to pull dynamically from dbo.DynamicTable.

@Zararia Acharki:

You are right. I can truncate the table for the first time. But I want to execute dynamically using SQL table dbo.DynamicTable using "SelectFromTable" column.

Thank you again for all your help.
Doug BishopDatabase Developer

Commented:
So, you want to truncate once only and then load into your target table from all the tables in source table(s) listed in DynamicTable? Or, is your example incorrect and you will be loading into separate target tables. It does not make sense to truncate the table to load subsequent tables when you just loaded data.

In other words, per your direction above, the steps would be:
  1. truncate BalanceAmtTable
  2. load BalanceAmtTable from AAAfiles
  3. truncate BalanceAmtTable
  4. load BalanceAmtTable from BBBfiles
  5. truncate BalanceAmtTable
  6. load BalanceAmtTable from CCCfiles
  7. ...
Unless there is some other interim processing going on after the load, you are going to truncate after each (except the final) load which means you lose the data just loaded.
Doug BishopDatabase Developer

Commented:
I am not a staunch nay-sayer regarding cursors as this is definitely a case for using one:

DECLARE @SQL VARCHAR(MAX);
DECLARE @SelectFromTable VARCHAR(128) = 'AAAfiles';
DECLARE @InsertIntoTable VARCHAR(128) = 'BalanceAmtTable';
DECLARE csrTables CURSOR LOCAL FAST_FORWARD FOR
    SELECT   SelectFromTable,
             InsertIntoTable
    FROM     dbo.DynamicTable
    ORDER BY SelectFromTable;

OPEN csrTables;
FETCH NEXT FROM csrTables INTO @SelectFromTable, @InsertIntoTable

WHILE @@FETCH_STATUS = 0
BEGIN
	SET @SQL = 'TRUNCATE TABLE dbo.' + @InsertIntoTable +'; INSERT INTO dbo.' + @InsertIntoTable + ' (Amt, BalanceAmt, Reasons, DateDue) SELECT Amt, BalanceAmt, Reasons, DateDue FROM dbo.' + @SelectFromTable + ' WHERE BalanceAmt >= Dateadd(Month, Datediff(Month, 0, DATEADD(m, -3, current_timestamp)), 0)  AND Amt = 0;'
	EXECUTE (@SQL);

	-- if there is other processing to do against the table you just loaded, it would go here
	FETCH NEXT FROM csrTables INTO @SelectFromTable, @InsertIntoTable
END

CLOSE csrTables
DEALLOCATE csrTables

-- post processing

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Author

Commented:
@DougBishop:

I just want to Truncate the Table first like this:

truncate table dbo.BalanceAmtTable. Since there is only table to delete and insert into.

then the next select query is:

Select  [SelectFromTable], [InsertIntoTable] from dbo.DynamicTable

I just don't know the query syntax.

Thank you again.
Doug BishopDatabase Developer

Commented:
Very minor change to above code:
DECLARE @SQL VARCHAR(MAX);
DECLARE @SelectFromTable VARCHAR(128) = 'AAAfiles';
DECLARE @InsertIntoTable VARCHAR(128) = 'BalanceAmtTable';
DECLARE csrTables CURSOR LOCAL FAST_FORWARD FOR
    SELECT   SelectFromTable,
             InsertIntoTable
    FROM     dbo.DynamicTable
    ORDER BY SelectFromTable;

OPEN csrTables;
FETCH NEXT FROM csrTables INTO @SelectFromTable, @InsertIntoTable
IF @@FETCH_STATUS = 0 
    EXECUTE ('TRUNCATE TABLE dbo.' + @InsertIntoTable +'; ')

WHILE @@FETCH_STATUS = 0
BEGIN
	SET @SQL = 'INSERT INTO dbo.' + @InsertIntoTable + ' (Amt, BalanceAmt, Reasons, DateDue) SELECT Amt, BalanceAmt, Reasons, DateDue FROM dbo.' + @SelectFromTable + ' WHERE BalanceAmt >= Dateadd(Month, Datediff(Month, 0, DATEADD(m, -3, current_timestamp)), 0)  AND Amt = 0;'
	EXECUTE (@SQL);

	-- if there is other processing to do against the table you just loaded, it would go here
	FETCH NEXT FROM csrTables INTO @SelectFromTable, @InsertIntoTable
END

CLOSE csrTables
DEALLOCATE csrTables

-- post processing

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Author

Commented:
@DougBishop:

I tested the code above but I have syntax error:

Incorrect syntax near the keyword 'INSERT'.
Msg 102, Level 15, State 1, Line 1
Incorrect syntax near ‘AMT'.
Msg 156, Level 15, State 1, Line 1
Incorrect syntax near the keyword 'SELECT'.
Msg 156, Level 15, State 1, Line 1
Incorrect syntax near the keyword 'WHERE'.
Msg 156, Level 15, State 1, Line 1

Thank you again for your help.
Database Developer
Commented:
This one is on us!
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Doug BishopDatabase Developer

Commented:
Here are the results of running the above code, as expected:
Src	Amt	BalanceAmt	Reasons	        DateDue
AAA	0.00	2018-11-02	reason 2 - AAA	2018-12-31
AAA	123.45	2018-11-01	reason 1 - AAA	2018-12-31
BBB	0.00	2018-11-04	reason 2 - BBB	2018-12-31
BBB	987.65	2018-11-03	reason 1 - BBB	2018-12-31
CCC	777.77	2018-11-05	reason 1 - CCC	2018-12-31
CCC	888.88	2018-11-06	reason 2 - CCC	2018-12-31
Out	0.00	2018-11-02	reason 2 - AAA	2018-12-31
Out	0.00	2018-11-04	reason 2 - BBB	2018-12-31

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Author

Commented:
@Doug Bishop:

I will test it and I will let you know.

Thank you again.

Author

Commented:
@Doug Bishop:

Thank you again for all your help.

To all Experts that helped me. Thank you.
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