Create trigger if column exists in SQL Server - sql

Question

How do I go about looping through all the tables that have the updated_at column? I figured out how to find all the tables that have the column using information_schema.columns like this:
SELECT TABLE_NAME FROM information_schema.columns WHERE COLUMN_NAME = 'updated_at'
But I have no idea how I would go about looping through all the tables to create the trigger to update the updated_at column to the current time with SYSDATETIMEOFFSET() when the row is updated?
EDIT: So I managed to figure out the iterating now using a cursor. but now im kind of confused about updating the date. So if I set an after update trigger to update the updated_at date, wouldn't that trigger an infinite loop?

Answer 1

Learning how to use system tables to help you write code dynamically is going to be important.
Also looping to do this is the worst thing ever.
SELECT
'CREATE TRIGGER schema.triggername
ON schema.tablename
AFTER UPDATE
AS
IF TRIGGER_NESTLEVEL() > 1
RETURN
UPDATE schema.tablename
SET RowUpdated = SYSDATETIMEOFFSET()
WHERE UniqueIdentifier/PrimaryKey IN
(
SELECT UniqueIdentifier/PrimaryKey
FROM Inserted
)
;
GO'
, 'UPDATE '+t.name+' SET '+c.name+' = SYSDATETIMEOFFSET(); '
FROM
sys.Tables t
INNER JOIN sys.columns c ON t.object_id =c.object_id
WHERE
c.name = 'RowLoaded'

Answer 2

#DougCoat's answer helped me come up with the create trigger and the looping was from this answer
DECLARE #TableName varchar(30)
DECLARE MY_CURSOR CURSOR
LOCAL STATIC READ_ONLY FORWARD_ONLY
FOR
SELECT TABLE_NAME FROM information_schema.columns WHERE COLUMN_NAME = 'updated_at'
OPEN MY_CURSOR
FETCH NEXT FROM MY_CURSOR INTO #TableName
WHILE ##FETCH_STATUS = 0
BEGIN
EXEC(
'CREATE TRIGGER tr_update_timestamp_' + #TableName + ' ON [' + #TableName +
'] AFTER UPDATE
AS
BEGIN
UPDATE [' + #TableName +
'] SET updated_at = SYSDATETIMEOFFSET()
WHERE [' + #TableName + '].id IN
(
SELECT i.id
FROM Inserted i
)
END'
)
FETCH NEXT FROM MY_CURSOR INTO #TableName
END
CLOSE MY_CURSOR
DEALLOCATE MY_CURSOR