SQL to Update records of one table with records from another table?

Question

I have two tables here both contain like lots of records in the tens of thousands. Now we have one main table whose schema is like this:

ID | Location Name | Label | Description | Longitude | Latitude

And we have another table with:

ID | Location Name | Longitude | Latitude

The issue is that the longitude and latitude entries in the first table are mostly wrong :( - the correct info is in the second table. Assuming that the IDs are corresponding to the same locations in both tables how can I fix up a query that updates the longitude and latitude field of every row in the first table based upon the entries in the second table where the IDs are the same. I am on a MySQL database.

EDIT

Note: Both tables have 20 000 and 50 000 rows respectively.

Answer 1

With MySQL 4.0+ you should be able to use the INNER JOIN syntax below:

UPDATE 
    new_table 
INNER JOIN 
    old_table ON (old_table.id = new_table.id)
SET 
    new_table.latitude = old_table.latitude,
    new_table.longitude = old_table.longitude;

Otherwise, you should also be able to do the following:

UPDATE 
    new_table 
SET 
    latitude = (SELECT latitude FROM old_table WHERE old_table.id = new_table.id),
    longitude = (SELECT longitude FROM old_table WHERE old_table.id = new_table.id);

Make sure that the ID columns in both tables have a unique index. If they are defined as a primary key, this is enough.

Answer 2

If ID's are primary keys / unique index you could use REPLACE

REPLACE INTO bad_latlng (id,name,label,descr,lat,lng)
SELECT
b.id,b.name,b.label,b.descr,g.lat,g.lng
FROM
bad_latlng b JOIN good_latlng g ON(b.id = g.id)