mysql how to replace a column content
Let's say you want to update id 27
Run this first
SELECT REPLACE(content,'http://www.abc.com/data/img','http://www.def.com/data/img') newurl
FROM Content_T1 WHERE id = 27;

If the result is correct, you can run
UPDATE Content_T1
SET content = REPLACE(content,'http://www.abc.com/data/img','http://www.def.com/data/img')
WHERE id = 27;
SELECT content FROM Content_T1 WHERE id = 27;

If the result is correct and you are ready to fix all of them, run this query without the WHERE clause:
UPDATE Content_T1
SET content = REPLACE(content,'http://www.abc.com/data/img','http://www.def.com/data/img');

Please, go to a test server and run this. When the results are correct ...
GIVE IT A TRY !!!