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UPDATE from a SELECT

Asked 2010-02-25T14:36:53.113
4351

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
sql sql-server t-sql sql-update
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4 Answers

6128
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'
answered 2010-02-25T14:39:55.367
199

Another possibility not mentioned yet is to just chuck the SELECT statement itself into a CTE and then update the CTE.

WITH CTE
     AS (SELECT T1.Col1,
                T2.Col1 AS _Col1,
                T1.Col2,
                T2.Col2 AS _Col2
         FROM   T1
                JOIN T2
                  ON T1.id = T2.id
         /*Where clause added to exclude rows that are the same in both tables
           Handles NULL values correctly*/
         WHERE EXISTS(SELECT T1.Col1,
                             T1.Col2
                       EXCEPT
                       SELECT T2.Col1,
                              T2.Col2))
UPDATE CTE
SET    Col1 = _Col1,
       Col2 = _Col2;

This has the benefit that it is easy to run the SELECT statement on its own first to sanity check the results, but it does requires you to alias the columns as above if they are named the same in source and target tables.

This also has the same limitation as the proprietary UPDATE ... FROM syntax shown in four of the other answers. If the source table is on the many side of a one-to-many join then it is undeterministic which of the possible matching joined records will be used in the Update (an issue that MERGE avoids by raising an error if there is an attempt to update the same row more than once).

answered 2011-11-06T00:18:38.863
76

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
answered 2012-06-11T16:58:24.900
65

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
answered 2011-09-08T21:35:34.463

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