Update multiple rows in a table from another table when condition exists

sql postgresql sql-update postgis
John picture John · Oct 13, 2012 · Viewed 40.1k times · Source

I have two tables.

Table1 contains companies whose locations are georeferenced with lat/lng coordinates in a column called the_geom

Table2 also contain the same companies from Table1, not georeferenced, along with hundreds of other companies whose addresses are georeferenced.

All I need to do is insert the_geom lat/lng values from Table1 companies into their corresponding entries in Table 2. The common denominator on which these inserts can be based on is the address column.

Simple question, I am sure, but I rarely use SQL.

Answer

Erwin Brandstetter picture Erwin Brandstetter · Oct 13, 2012

Assuming that by

insert "the_geom" lat/lng values

you actually mean to update existing rows in table2:

UPDATE table2 t2
SET    the_geom = t1.the_geom
FROM   table1 t1
WHERE  t2.address = t1.address
AND    t2.the_geom IS DISTINCT FROM t1.the_geom; -- avoid empty updates

Also assuming that the address column has UNIQUE values.
Details about UPDATE in the excellent manual here.

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