Implementing a for loop in SQL to update rows - sql

Question

How do I write the below code in SQL? The query would update each column in the table from the result.
DECLARE #table_list NVARCHAR -- What data type do I use to hold a list?
DECLARE #column_list NVARCHAR
SET #table_list = (SELECT DISTINCT [ID_TABLE_NAME] FROM dbo.VMO) -- there are more than one results
SET #column_list = (SELECT DISTINCT [USR_COL_NAME] FROM dbo.VMO) -- there are more than one results
foreach(#table IN #table_list)
{
foreach(#column IN #column_list)
{
UPDATE #table
SET #column = '101211'
WHERE #column = '10120'
}
}

Answer 1

You can use CURSORs to act like a foreach loop:
DECLARE #table NVARCHAR(255)
DECLARE #column NVARCHAR(255)
DECLARE OUTER_CURSOR CURSOR
FOR SELECT DISTINCT [ID_TABLE_NAME] FROM dbo.VMO
OPEN OUTER_CURSOR
FETCH NEXT FROM OUTER_CURSOR INTO #table
WHILE (##FETCH_STATUS <> -1)
BEGIN
DECLARE INNER_CURSOR CURSOR
FOR SELECT DISTINCT [USR_COL_NAME] FROM dbo.VMO
OPEN INNER_CURSOR
FETCH NEXT FROM INNER_CURSOR INTO #column
WHILE (##FETCH_STATUS <> -1)
BEGIN
DECLARE #strQuery NVARCHAR(MAX)
SET #strQuery = 'UPDATE [' + #table + '] SET [' + #column + '] = ''101211'' WHERE [' + #column + '] = ''10120'';'
EXEC(#strQUERY)
FETCH NEXT FROM INNER_CURSOR INTO #column
END
CLOSE INNER_CURSOR
DEALLOCATE INNER_CURSOR
FETCH NEXT FROM OUTER_CURSOR INTO #table
END
CLOSE OUTER_CURSOR
DEALLOCATE OUTER_CURSOR

Answer 2

T-SQL doesn't have a FOR loop, perhaps it has a WHILE (Transact-SQL)
Use SQL like below:
DECLARE #table_list NVARCHAR -- What data type do I use to hold a list?
DECLARE #column_list NVARCHAR
SET #table_list = (SELECT DISTINCT [ID_TABLE_NAME] FROM dbo.VMO) -- there are more than one results
SET #column_list = (SELECT DISTINCT [USR_COL_NAME] FROM dbo.VMO) -- there are more than one results
WHILE #column_list > #table_list
BEGIN
UPDATE #table
SET #column = '101211'
WHERE #column = '10120'
END;