How do I UPDATE from a SELECT in SQL Server?

In **SQL Server**, it is possible to insert rows into a table with an `INSERT.. SELECT` statement:

INSERT INTO Table (col1, col2, col3)
SELECT col1, col2, col3
FROM other_table
WHERE sql = 'cool'

Is it also possible to _update_ a table with `SELECT`? I have a temporary table containing the values and would like to update another table using those values. Perhaps something like this:

UPDATE Table SET col1, col2
SELECT col1, col2
FROM other_table
WHERE sql = 'cool'
WHERE Table.id = other_table.id

I add this only so you can see a quick way to write it so that you can check what will be updated before doing the update.

UPDATE Table
SET Table.col1 = other_table.col1,
Table.col2 = other_table.col2
--select Table.col1, other_table.col,Table.col2,other_table.col2, *
FROM Table
INNER JOIN other_table
ON Table.id = other_table.id

This may be a niche reason to perform an update (for example, mainly used in a procedure), or may be obvious to others, but it should also be stated that you can perform an update-select statement without using join (in case the tables you're updating between have no common field).


update
Table
set
Table.example = a.value
from
TableExample a
where
Table.field = *key value* -- finds the row in Table
AND a.field = *key value* -- finds the row in TableExample a

For the record (and others searching like I was), you can do it in MySQL like this:

UPDATE first_table, second_table
SET first_table.color = second_table.color
WHERE first_table.id = second_table.foreign_id

Here is another useful syntax:

UPDATE suppliers
SET supplier_name = (SELECT customers.name
FROM customers
WHERE customers.customer_id = suppliers.supplier_id)
WHERE EXISTS (SELECT customers.name
FROM customers
WHERE customers.customer_id = suppliers.supplier_id);

It checks if it is null or not by using "WHERE EXIST".

One way

UPDATE t
SET t.col1 = o.col1,
t.col2 = o.col2
FROM
other_table o
JOIN
t ON t.id = o.id
WHERE
o.sql = 'cool'

UPDATE table AS a
INNER JOIN table2 AS b
ON a.col1 = b.col1
INNER JOIN ... AS ...
ON ... = ...
SET ...
WHERE ...

UPDATE
Table_A
SET
Table_A.col1 = Table_B.col1,
Table_A.col2 = Table_B.col2
FROM
Some_Table AS Table_A
INNER JOIN Other_Table AS Table_B
ON Table_A.id = Table_B.id
WHERE
Table_A.col3 = 'cool'

The other way is to use a derived table:

UPDATE t
SET t.col1 = a.col1
,t.col2 = a.col2
FROM (
SELECT id, col1, col2 FROM @tbl2) a
INNER JOIN @tbl1 t ON t.id = a.id

-------------------

Sample data

DECLARE @tbl1 TABLE (id INT, col1 VARCHAR(10), col2 VARCHAR(10))
DECLARE @tbl2 TABLE (id INT, col1 VARCHAR(10), col2 VARCHAR(10))

INSERT @tbl1 SELECT 1, 'a', 'b' UNION SELECT 2, 'b', 'c'

INSERT @tbl2 SELECT 1, '1', '2' UNION SELECT 2, '3', '4'

UPDATE t
SET t.col1 = a.col1
,t.col2 = a.col2
FROM (
SELECT id, col1, col2 FROM @tbl2) a
INNER JOIN @tbl1 t ON t.id = a.id

SELECT * FROM @tbl1
SELECT * FROM @tbl2

The following example uses a derived table, a SELECT statement after the FROM clause, to return the old and new values for further updates:

UPDATE x
SET x.col1 = x.newCol1,
x.col2 = x.newCol2
FROM (SELECT t.col1,
t2.col1 AS newCol1,
t.col2,
t2.col2 AS newCol2
FROM [table] t
JOIN other_table t2
ON t.ID = t2.ID) x