patch datetime in varchar column - sql

Question

i have about 12 tables i need to iterate thru and update all datetime fields (which is a varchar type) check if it's a date and if so, add 5hrs to account for utc adjustment or if it's an invalid date just set it to null. Below is a template I came up with. Just wondering if there are some other ways to do this?
update Tables_1
set releasedate = CASE ISDATE(releasedate)
WHEN 1 THEN DATEADD(HH, 5, releasedate)
ELSE NULL
END,
returndate = CASE ISDATE(returndate)
WHEN 1 THEN DATEADD(HH, 5, returndate)
ELSE NULL
END
given: sql server 2008, i know the columns and tables already that have the datetime type stored as varchar.
bonus request to add another check. If it is a date and the time is not specified, set the time to 5:00 AM

Answer 1

If they all end with date you could build it dynamically:
DECLARE #sql NVARCHAR(MAX) = N'';
SELECT #sql += ', ' + name = CASE ISDATE(' + name + ') WHEN 1 THEN
DATEADD(HOUR, 5, ' + name + ' ELSE NULL END'
FROM sys.columns
WHERE name LIKE '%date' AND [object_id] = OBJECT_ID('dbo.Tables_1');
SELECT #sql = 'UPDATE dbo.Tables_1 SET ' + STUFF(#sql, 1, 1, N'');
PRINT #sql;
-- EXEC sp_executesql #sql;
Now if you want to do that for 12 tables, you could just do this in a loop, e.g.
DECLARE #t SYSNAME, #sql NVARCHAR(MAX);
DECLARE c CURSOR LOCAL STATIC FORWARD_ONLY READ_ONLY
FOR
SELECT name FROM sys.tables
WHERE name IN ('Tables_1' --, other tables
);
OPEN c;
FETCH NEXT FROM c INTO #t;
WHILE ##FETCH_STATUS = 0
BEGIN
SELECT #sql = ', ' + name = CASE ISDATE(' + name + ') WHEN 1 THEN
DATEADD(HOUR, 5, ' + name + ' ELSE NULL END'
FROM sys.columns
WHERE name LIKE '%date' AND [object_id] = OBJECT_ID(#t);
SELECT #sql = 'UPDATE ' + #t + ' SET ' + STUFF(#sql, 1, 1, N'');
PRINT #sql;
-- EXEC sp_executesql #sql;
FETCH NEXT FROM c INTO #t;
END
CLOSE c;
DEALLOCATE c;