Adding (results of a query) to an existing table - mysql

Question

So i have the following problem. I have 2 tables (Users: 100 rows and geo-zipcodes: 450k rows) and I want to update my users table to display the lon and lat if the zipcode is filled in. When it's not filled in i want the lon/lat to display NULL. How do I achieve this?
I do this in MySQL using the standard provided MySQL workbench.
+CURRENT SITUATION----+------+
| id | zipcode | lon | lat |
+----+---------+------+------+
| 88 | 3531EK | NULL | NULL |
| 89 | 5691JN | NULL | NULL |
| 90 | 5701NR | NULL | NULL |
| 91 | 3531EK | NULL | NULL |
| 92 | 5691JN | NULL | NULL |
| 93 | NULL | NULL | NULL |
| 94 | NULL | NULL | NULL |
| 95 | NULL | NULL | NULL |
| 96 | NULL | NULL | NULL |
| 97 | NULL | NULL | NULL |
+----+---------+------+------+
+FUTURE SITUATION------------------+-----------------+
| id | zipcode | lat | lon |
+-----+---------+------------------+-----------------+
| 583 | NULL | NULL | NULL |
| 632 | NULL | NULL | NULL |
| 797 | 4194WD | 51.8724978062918 | 5.2758839816285 |
| 812 | 9723ZT | 53.2067353295688 | 6.5886266741127 |
| 782 | 5617BD | 51.4471593854488 | 5.4566869544855 |
| 799 | NULL | NULL | NULL |
| 800 | 5623ET | 51.4618395108795 | 5.4733910341403 |
| 179 | 5709BN | 51.4752182995384 | 5.7022349534995 |
| 112 | 5701CN | 51.4759330063412 | 5.6780783810570 |
| 90 | 5701NR | 51.4775509176254 | 5.6576320175919 |
+-----+---------+------------------+-----------------+

Answer 1

In MySQL, you can do this with a join:
update users u join
zipcodes z
on u.zipcode = z.zipcode
set u.lat = z.lat, u.lon = z.lon;
However, I don't see why this is necessary. Why not just look up the coordinates using the zip code table when you need it? There might be good reasons -- for instance, you might have other sources of coordinates. But if the zip code is the only source, then there is no need to store the same information in two places.