MSSQL How to copy data from one table to another with a condition

Question

I'm trying to update table a with data from some of the columns in table b. Column names are matching in both tables, cannot figure out the syntax, can anyone help?

This is what I want to do (expressed out-of-syntax):

UPDATE table_a SET table_a.col1 = table_b.col1, table_a.col2 = table_b.col2 WHERE table_a.id = table_b.id

Maybe (probably) I would need some kind of JOIN-clause, but I haven't gotten my head around those yet.... :-/

Answer 1

You can update your table using a JOIN of the two tables:

UPDATE table_a a
INNER JOIN table_b b ON a.id = b.id
SET a.col1 = b.col1, a.col2 = b.col2

I see you are on MYSQL. Not sure if the version above works. If not, try:

UPDATE table_a a
INNER JOIN table_b b
SET a.col1 = b.col1, a.col2 = b.col2
WHERE a.id = b.id

Answer 2

Ok, so I found it myself... :-)

MERGE (without using the WHEN NOT MATCHED clause)is the answer to my problem.

My solution:

MERGE INTO table_a USING table_b ON a.id=b.id WHEN MATCHED THEN UPDATE SET col1 = b.col1, col2 = b.col2;