如何在sql中更新条目？

I cant figure it out. I have this variable (for example):

$level_building = "test,";

and this sql string:

mysql_query("UPDATE info_buildings SET building='$level_building' + building WHERE nick='$nick'") or die(mysql_error());

all i want to do is to add new text test, after existing text, but after updating it, sql shows 0 (building=0).. My sql output should look like this test,test,test,... Example: building=test,test,test, and each time i use sql string UPDATE it should write new test text in the same building string.. Sorry for bad english i hope you understand this.

In MySQL, + is for arithmetic addition. To concatenate strings, use CONCAT():

UPDATE info_buildings 
SET building = CONCAT('$level_building', building)
WHERE nick = '$nick'

All the MySQL string functions can be found here.

However, I recommend you reconsider your table design. Putting comma-separated lists in a single column is usually poor design. You should use a separate table with a row for each value.