PostgreSQL UPDATE substring replacement

问题

I have a few rows in a test database where there are dollar signs prefixed to the value. I want to UPDATE the values in the name row of the test1 table however when I threw the following query together it emptied the six rows of data in the name column...

UPDATE test1 SET name=overlay('$' placing '' from 1 for 1);

So "$user" became "" when I intended for that column/row value to become "user".

How do I combine UPDATE and a substr replacement without deleting any of the other data?

If there isn't a dollar sign I want the row to remain untouched.

The dollar sign only occurs as the first character when it does occur.

回答1:

If you want to replace all dollar signs, use this:

update test1 
   set name = replace(name, '$', '');

If you want to replace the $ only at the beginning of the value you can use substr() and a where clause to only change those rows where the column actually starts with a $

update test1 
    set name = substr(name, 2)
where name like '$%';

来源：https://stackoverflow.com/questions/27152413/postgresql-update-substring-replacement